Stacked arrangement and method of forming the same

Abstract

Various embodiments may relate to a stacked arrangement. The stacked arrangement may include a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers including a hybrid organic-inorganic iodine-based metal halide perovskite material. The stacked arrangement may also include a plurality of secondary semiconducting material layers including a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers. Each of the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers may have a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine- based metal halide perovskite material. Each of the plurality of secondary semiconductor material layers may have a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer.

Description

STACKED ARRANGEMENT AND METHOD OF FORMING THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of Singapore application No. 10202402246S filed July 26, 2024, the contents of it being hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] Various embodiments of this disclosure may relate to a stacked arrangement. Various embodiments of this disclosure may relate to a method of forming a stacked arrangement.BACKGROUND

[0003] Quantum confinement can boost the optoelectronic properties of semiconductors; such as tunable bandgap, increased exciton binding energy, and higher luminescence efficiency. Quantum confinement is achieved when at least one of a material’s spatial dimensions approaches its exciton Bohr diameter. Multiple quantum wells (MQWs) are fonned by alternately stacking ultrathin films of semiconductors with different bandgaps. Conventionally, the wide bandgap material is called a barrier, whereas the narrow bandgap is the well. When the barrier and well material have significantly different dielectric constants, the effects of quantum confinement will be boosted by dielectric confinement.

[0004] The MQW structure has been developed based on different semiconducting materials (i.e., III-V materials) to enhance their optoelectronic properties and improve device performance significantly. Indeed, by including MQWs as “spectrum filling” layers in multijunction devices, III-V-based solar cells have achieved power conversion efficiencies of over 39%. For light-emitting applications, MQW’s inherent bandgap tunability enabled a green light-emitting diode with over 50% external quantum efficiency.

[0005] Structurally confined perovskite MQWs can be constructed by thermal evaporation, which guarantees a high degree of thickness control and multilayer additivity over a potentially large area. To date, perovskite MQWs have been reported exclusively based on bromide (Br) inorganic perovskite (caesium lead bromide or CsPbB ) and using three organic barriers,showing very promising results for the tuning of the optoelectronic properties in these structuresSUMMARY

[0006] Various embodiments may relate to a stacked arrangement. The stacked arrangement may include a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers including a hybrid organic-inorganic iodine-based metal halide perovskite material. The stacked arrangement may also include a plurality of secondary semiconducting material layers including a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers. Each of the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers may have a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine- based metal halide perovskite material. Each of the plurality of secondary semiconductor material layers may have a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer.

[0007] Various embodiments may relate to a method of forming a stacked arrangement. The method may include forming a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers including a hybrid organic-inorganic iodine-based metal halide perovskite material. The method may also include forming a plurality of secondary semiconducting material layers including a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers. Each of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers may have a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine-based metal halide perovskite material. Each of the plurality of secondary semiconductor material layers may have a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead generally being placed upon illustrating the principles of various embodiments. In the following description, various embodiments of the invention are described with reference to the following drawings.FIG. 1 shows a general illustration of a stacked arrangement according to various embodiments. FIG. 2 shows a general illustration of a method of forming a stacked arrangement according to various embodiments.FIG. 3A shows an optical microscopy image of methylammonium lead iodide (CHsNHsPbls or MAPbL) deposited on indium tin oxide (film thicknesses from left to right: 3 nm, 5 nm, 7 nm, 10 nm and 100 nm).FIG. 3B shows a plot of halide ionic radius (in nanometres or nm) as a function of photoluminescence PL peak shift (in electron volts or eV) illustrating potential bandgap widening upon quantization for methylammonium lead iodide (MAPb^-based perovskite dependent on the halide ionic radius according to various embodiments.FIG. 3C shows a schematic illustrating multiple quantum well (MQW) deposition using thermal evaporation cycles according to various embodiments.FIG. 3D shows schematics and simplified band diagrams of type-1 and type-11 multiple quantum well (MQW) stacked arrangements constructed of methylammonium lead iodide (MAPbL) with (left) bathocuproine (BCP) and (right) lead phthalocyanine (PbPC), respectively, according to various embodiments.FIG. 3E shows a schematic illustrating the atomic force microscopy (AFM) surface height maps of 5 nm layers of (left) lead phthalocyanine (PbPC) and (right) bathocuproine (BCP) deposited through thermal evaporation onto low roughness indium tin oxide (ITO) substrates according to various embodiments.FIG. 3F shows a table illustrating the measured methylammonium lead iodide (CHjNHjPbh or M APbh) film thickness for various deposition times according to various embodiments. FIG. 3G shows a plot of methylammonium lead iodide MAPbh thickness (in nanometres or nm) as deposition time (in seconds or s) illustrating the linear relationship between themeasured thickness of evaporated MAPbh films and deposition time according to various embodiments.FIG. 3H shows a cross-sectional scanning electron microscope (SEM) image of a type-I multiple quantum well (MQW) stacked arrangement including alternating layers of methylammonium lead iodide (MAPbh) and bathocuproine (BCP) according to various embodiments.FIG. 4A shows (left) a schematic of methylammonium lead iodide (MAPbh) layer on low roughness indium tin oxide (ITO) / glass; (middle) a plot of offset normalized intensity as a function of angle 29 (in degrees or °) illustrating the X-ray diffraction patterns of different thicknesses of methylammonium lead iodide (MAPbh) of the arrangement shown on the left; and (right top) atomic force microscopy (AFM) surface height map of a 5 nm methylammonium lead iodide (MAPbh) layer of the arrangement shown on the left.FIG. 4B shows (left) a schematic of methylammonium lead iodide (MAPbl ;) layer on bathocuproine (BCP)Zindium tin oxide (ITO)Zglass; (middle) a plot of offset normalized intensity as a function of angle 29 (in degrees or °) illustrating the X-ray diffraction patterns of different thicknesses of methylammonium lead iodide (MAPbh) of the arrangement shown on the left; and (right top) atomic force microscopy (AFM) surface height map of a 5 nm methylammonium lead iodide (MAPbh) layer of the arrangement shown on the left.FIG. 4C shows (left) a schematic of methylammonium lead iodide (MAPbh) layer on lead phthalocyanine (PbPC)Zindium tin oxide (ITO)Zglass; (middle) a plot of offset normalized intensity as a function of angle 29 (in degrees or °) illustrating the X-ray diffraction patterns of different thicknesses of methylammonium lead iodide (MAPbh) of the arrangement shown on the left; and (right top) atomic force microscopy (AFM) surface height map of a 5 nm methylammonium lead iodide (MAPbh) layer of the arrangement shown on the left.FIG. 5A shows a plot of absorbance as a function of wavelength (in nanometres or nm) illustrating the absorbance spectra of methylammonium lead iodide (MAPbh) layers of various thicknesses deposited on 5 nm bathocuproine (BCP) according to various embodiments.FIG. 5B shows a plot of normalised absorbance as a function of wavelength (in nanometres or nm) illustrating the normalised absorbance spectra of methylammonium lead iodide (MAPbh,) layers of various thicknesses deposited on 5 nm bathocuproine (BCP) according to various embodiments.FIG. 6A shows (left) energy band diagram, (middle) a plot of normalised photoluminescence (PL) as a function of energy (in electron volts or eV) illustrating PL spectra of arrangements with different methylammonium lead iodide (MAPbL) thicknesses, and (right) a plot of methylammonium lead iodide (MAPbL) band gap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbL) thickness (in nanometres or nm) of type-I methylammonium lead iodide (MAPbL) / bathocuproine (BCP) (5 nm) single quantum well (SQW) stacked arrangement according to various embodiments.FIG. 6B shows (left) energy band diagram, (middle) a plot of normalised photoluminescence (PL) as a function of energy (in electron volts or eV) illustrating PL spectra of arrangements with different methylammonium lead iodide (MAPbL) thicknesses, and (right) a plot of ethyl ammonium lead iodide (MAPbL) band gap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbL) thickness (in nanometres or nm) of type-II methylammonium lead iodide (MAPbL) / lead phthalocyanine (PbPC) (5 nm) single quantum well (SQW) stacked arrangement according to various embodiments.FIG. 60 shows (a) a plot of bandgap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbL) thickness (in nanometres or nm) comparing bandgap variations of bare MAPbL and type-I methylammonium lead iodide (MAPbL) / bathocuproine (BCP) single quantum well (SQW) stacked arrangement according to various embodiments; and (b) a plot of bandgap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbL) thickness (in nanometres or nm) comparing bandgap variations of bare MAPbL and type-11 methylammonium lead iodide (MAPbL) / lead phthalocyanine (PbPC) single quantum well (SQW) stacked arrangement according to various embodiments.FIG. 6D shows a plot of integrated photoluminescence (PL) intensity as a function of methylammonium lead iodide (MAPbL) thickness (in nanometres or nm) illustrating integrated PL intensity normalised to the bulk (50 nm) of each type: methylammonium lead iodide (MAPbL), type-I single quantum well (SQW) stacked arrangement, and type-II single quantum well (SQW) stacked arrangement according to various embodiments.FIG. 6E shows a plot of photoluminescence (PL) peak Full Width at Half Maximum (FWHM) (in degrees or °) as a function of methylammonium lead iodide (MAPbL) thickness (in nanometres or nm) illustrating PL peak broadening with decreasing MAPbL layer thickness for bare MAPbL (black dots), type-I single quantum well (SQW) stacked arrangement (lightsquares), and type-II single quantum well (SQW) stacked arrangement (grey hexagons) according to various embodimentsFIG. 6F shows the energy band diagrams of a type-I methylammonium lead iodide (MAPbh) multiple quantum well (MQW) / bathocuproine (BCP) stacked arrangement according to various embodiments, and a type-II methylammonium lead iodide (MAPbI3) multiple quantum well (MQW) / lead phthalocyanine (PbPC) stacked arrangement according to various embodiments.FIG. 7A shows a schematic of a photodetector including the stacked arrangement according to various embodiments.FIG. 7B shows (left) a plot of photocurrent at 5V (in nano-Amperes or nA) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating photocurrent ( / Ph) of type-I multiple quantum well (light squares) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of photocurrent at 5 V (in nano-Amperes or nA) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating photocurrent (7Ph) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide ('MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of photocurrent at 5 V (in nano-Amperes or nA) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating photocurrent ( / Ph) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.FIG. 7C shows (left) a plot of responsivity (in micro-Amperes per Watt or pA / W) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating calculated responsivity ( / ?) of type-I multiple quantum well (light squares) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of responsivity (in micro-Amperes per Watt or pA / W) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating calculated responsivity (R) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of responsivity (in micro- Amperes per Watt or pA / W) as a function of light intensity (in milli-Watts per squarecentimetre or mW / cm2) illustrating calculated responsivity (R) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.FIG. 7D shows (left) a plot of external quantum efficiency EQE (in percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating EQE of type-I multiple quantum well (light squares) and methyl ammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of external quantum efficiency EQE (in percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating EQE of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of external quantum efficiency EQE (in - I O'4percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating EQE of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.FIG. 7E shows (left) a plot of specific detectivity (inzl 0 Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating specific detectivity of type-I multiple quantum well (light squares) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments, (middle) a plot of external specific detectivity (in * 106Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating specific detectivity of type-II multiple quantum well (light hexagons) and methyl ammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of specific detectivity (inZI O5Jones) as a function of light intensity (in milli- Watts per square centimetre or mW / cm2) illustrating specific detectivity of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.FIG. 7F shows a table illustrating the figures of merit of various photodetectors according to various embodiments. The subscript vis refers to visible (525 nm) excitation, with a light intensity of 60 mW / cm2. The subscript IR refers to near-infrared (850 nm) excitation, with a light intensity of 147 mW / cm2. Photocurrent (TpQ and responsivity R) were extracted at an applied bias of +5 V.FIG. 7G shows plots of absorbance as a function of wavelength (in nanometres or nm) illustrating the absorbance spectra of methylammonium lead iodide (MAPbh) films, lead phthalocyanine (PbPC) / methylammonium lead iodide (MAPbh) stacked arrangement, lead phthalocyanine (PbPC) / methylammonium lead iodide (MAPbh) / lead phthalocyanine (PbPC) single quantum well stacked arrangement and lead phthalocyanine (PbPC) films in which each MAPbh film or layer is (a) 7 nm, (b) 5 nm and (c) 3 nm thick according to various embodiments. Each PbPC layer or film is 5 nm thick.FIG. 7H shows plots of current (in nano-Amperes or nA) as a function of voltage (in volts or V) illustrating (a) measured output current from the 20 nm methylammonium lead iodide (MAPbh) film under dark and 850 nm infrared light excitation according to various embodiments; and (b) measured output current from the 25 nm lead phthalocyanine (PbPC) film under dark and 525 nm green light excitation according to various embodiments.FIG. 8A shows a plot of photocurrent at 5V (in nano-Amperes or nA) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the photocurrents of a type-II methylammonium lead iodide (MAPbh) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments.FIG. 8B shows a plot of responsivity (in micro- Amperes per Watt or pA / W) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the responsivities of a type-II methylammonium lead iodide (MAPbh) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments.FIG. 8C shows a plot of external quantum efficiency EQE (in - I O'1percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the EQEs of a type-II methylammonium lead iodide (MAPbh) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments.FIG. 8D shows a plot of specific detectivity (in * 10' Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the specific detectivities of a type- II methylammonium lead iodide (MAPbh) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments.DESCRIPTION

[0009] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0010] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0011] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0012] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance, e.g., within 10% of the specified value.

[0013] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0014] By “comprising” it is meant including, but not limited to, whatever follows the word “comprising”. Thus, use of the term “comprising” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present.

[0015] By “consisting of’ it is meant including, and limited to, whatever follows the phrase “consisting of’. Thus, the phrase “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present.

[0016] Embodiments described in the context of one of the stacked arrangements are analogously valid for the other stacked arrangements. Similarly, embodiments described in the context of a method are analogously valid for a stacked arrangement, and vice versa.

[0017] However, hybrid organic-inorganic perovskite compositions exhibit better performance in solar cells and light-emitting diodes, providing a motivation to investigate MQWs composed of such hybrid perovskite as well.

[0018] FIG. 1 shows a general illustration of a stacked arrangement according to various embodiments. The stacked arrangement may include a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102 including a hybrid organic-inorganic iodine- based metal halide perovskite material. The stacked arrangement may also include a plurality of secondary semiconducting material layers 104 including a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102. Each of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102 may have a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine-based metal halide perovskite material. Each of the plurality of secondary semiconductor material layers 104 may have a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer

[0019] In other words, various embodiments may relate to a stacked arrangement including alternating hybrid organic-inorganic iodine-based metal halide perovskite layers 102 and secondary semiconducting material layers 104. Each hybrid organic-inorganic iodine-based metal halide perovskite layer 102 may have a thickness less than or equal to its exciton Bohr diameter (e.g., 5.6 nm), while each secondary semiconductor material layer 104 may have a thickness (e.g., 5 nm or less) such that charge carriers can pass through via quantum tunnelling.

[0020] For avoidance of doubt, FIG. 1 seeks to illustrate some features of a stacked arrangement, and is not intended to limit, e.g., the number, dimensions, orientation, arrangement etc. of the various embodiments For instance, while FIG. 1 shows three hybrid organic-inorganic iodine-based metal halide perovskite layers 102, and two secondary semiconducting material layers 104, various other embodiments may relate to a stacked arrangements including any suitable number of hybrid organic-inorganic iodine-based metal halide perovskite layers 102, and any suitable number of secondary semiconducting material layers 104. While FIG. 1 shows hybrid organic-inorganic iodine-based metal halide perovskite layers 102 as the topmost and bottommost layers, in various other embodiments, the topmost and / or the bottommost layer may be a secondary semiconducting material layer 104.

[0021] In various embodiments, the secondary semiconducting material may have a bandgap different to a bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

[0022] In various embodiments, the hybrid organic-inorganic iodine-based metal halide perovskite layers 102 may be methylammonium lead iodide (MAP BL,) layers.

[0023] In various embodiments, the stacked arrangement may have a type-1 alignment structure. The bandgap of the secondary semiconducting material may have highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) respectively lower and higher than highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material In other words, the LUMO of the secondary semiconducting material layers 104 may be higher compared to the LUMO of the hybrid organic-inorganic iodine-based metal halide perovskite layers 102, while the HOMO of the secondary semiconducting material layers 104 may be lower compared to the HOMO of the hybrid organic-inorganic iodine-based metal halide perovskite layers 102. In various embodiments, the plurality of secondary semiconducting material layers may include bathocuproine (BCP) In various embodiments, upon irradiation of light onto the stacked arrangement, electrons generated and holes generated may be in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102, thereby increasing a recombination rate between the electrons and the holes and improving emissive properties of the stacked arrangement.

[0024] In various embodiments, the stacked arrangement may have a type-II alignment configuration, more specifically a type-IL alignment configuration. The bandgap of the secondary semiconducting material may have highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both higher than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material. In other words, the LUMO of the secondary semiconducting material layers 104 may be higher compared to the LUMO of the hybrid organic-inorganic iodine-based metal halide perovskite layers 102, and the HOMO of the secondary semiconducting material layers 104 may also be higher compared to the HOMO of the hybrid organic-inorganic iodine-based metal halide perovskite layers 102. In various embodiments, the plurality of secondary semiconducting material layers may include lead phthalocyanine (PbPC). In various embodiments, upon irradiation of lightonto the stacked arrangement, electrons generated may be segregated in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102 and holes generated may be segregated in the plurality of secondary semiconducting material layers 104, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

[0025] In various embodiments, the stacked arrangement may have a type-11 alignment configuration, more specifically a type-IIvalignment configuration. The bandgap of the secondary semiconducting material may have highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both lower than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material In other words, the LUMO of the secondary semiconducting material layers 104 may be lower compared to the LUMO of the hybrid organic-inorganic iodine-based metal halide perovskite layers 102, and the HOMO of the secondary semiconducting material layers 104 may also be lower compared to the HOMO of the hybrid organic-inorganic iodine-based metal halide perovskite layers 102. Upon irradiation of light onto the stacked arrangement, holes generated may be segregated in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102 and electrons generated may be segregated in the plurality of secondary semiconducting material layers 104, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

[0026] In various embodiments, for type-II alignment structure, the stacked arrangement may be configured to absorb or emit from visible to infrared light. The plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers 102 may be configured to absorb or emit visible light, while the plurality of the secondary semiconductor material layers 104 may be configured to absorb or emit infrared light.

[0027] In various embodiments, each of the plurality of hybrid organic-inorganic iodine- based metal halide perovskite layers 102 may be a continuous layer, and each of the plurality of secondary semiconducting material layers 104 may be a continuous layer.

[0028] FIG. 2 shows a general illustration of a method of forming a stacked arrangement according to various embodiments. The method may include, in 202, forming a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers including a hybrid organic-inorganic iodine-based metal halide perovskite material. The method may also include,in 204, forming a plurality of secondary semiconducting material layers including a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers. Each of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers may have a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine-based metal halide perovskite material. Each of the plurality of secondary semiconductor material layers may have a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer.

[0029] In other words, various embodiments may relate to a method of forming a stacked arrangement including alternate hybrid organic-inorganic iodine-based metal halide perovskite layers and secondary semiconducting material layers.

[0030] For avoidance of doubt, FIG. 2 is not intended to limit the sequence of the various steps. For instance, in various embodiments, a first layer of the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers may be formed first, followed by a first layer of the plurality of secondary semiconducting material layers on the first layer of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers. A second layer of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers may then be formed on the first layer of the plurality of secondary semiconducting material layers, followed by a second layer of the plurality of secondary semiconducting material layers on the second layer of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers, and so on. In various other embodiments, a first layer of the plurality of secondary semiconducting material layers may be formed first, followed by a first layer of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers on the first layer of the plurality of secondary semiconducting material layers A second layer of the plurality of secondary semiconducting material layers may then be formed on the first layer of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers, followed by a second layer of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers on the second layer of the plurality of secondary semiconducting material layers

[0031] In various embodiments, the plurality of secondary semiconducting material layers and the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers may be formed using a vacuum based deposition process.

[0032] In various embodiments, the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers may be formed by co-evaporation of a first source and a second source in the vacuum based deposition process. In various embodiments, the first source may be methylammonium iodide (MAI), and the second source may be lead iodide (Pbb). The MAI may be heated to a temperature at or above 350 °C, while the lead iodide (Pbl?) may be heated to a temperature at or above 130 °C.

[0033] In various embodiments, the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers including the hybrid organic-inorganic iodine-based metal halide perovskite material may be formed in a first thermal evaporation chamber. The plurality of secondary semiconducting material layers including the secondary semiconducting material may be formed in the first thermal evaporation chamber or in a second thermal evaporation chamber different from the first thermal evaporation chamber.

[0034] In various embodiments, the semiconducting material may have a bandgap different to a bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

[0035] In various embodiments, the stacked arrangement may have a type-I alignment structure. The bandgap of the secondary semiconducting material may have highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) respectively lower and higher than highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material. In various embodiments, the plurality of secondary semiconducting material layers may include bathocuproine (BCP). In various embodiments, upon irradiation of light onto the stacked arrangement, electrons generated and holes generated may be in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers, thereby increasing a recombination rate between the electrons and the holes and improving emissive properties of the stacked arrangement.

[0036] In various embodiments, the stacked arrangement may have a type-II alignment configuration, more specifically a type-IIcalignment configuration. The bandgap of the secondary semiconducting material may have highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both higher than respective highest occupiedmolecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material In various embodiments, the plurality of secondary semiconducting material layers may include lead phthalocyanine (PbPC). In various embodiments, upon irradiation of light onto the stacked arrangement, electrons generated may be segregated in the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers and holes generated may be segregated in the plurality of secondary semiconducting material layers, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

[0037] In various embodiments, the stacked arrangement may have a type-II alignment configuration, more specifically a type-IIvalignment configuration. The bandgap of the secondary semiconducting material may have highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both lower than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material. Upon irradiation of light onto the stacked arrangement, holes generated may be segregated in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers and electrons generated may be segregated in the plurality of secondary semiconducting material layers, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

[0038] Various embodiments may relate to a perovskite multiple quantum well (MQW) stacked arrangement including methylammonium lead iodide (CHJMLPbL or MAPbL) layers. Iodine-based perovskites, thanks to the larger halide radius, can reach a greater extent of quantization and further reveal the potential of perovskite MQWs. MAPbL may be paired with bathocuproine (BCP) and lead phthalocyanine (PbPC) to construct type-I and type-II quantum well (QW) stacks, respectively. Optical measurements show ~50 times higher photoluminescence intensity and ~ 18 times faster recombination rate in type-I single quantum wells (SQWs) according to various embodiments, as the MAPbL layer is thinned from bulk into the quantum confined regime. In contrast, the emission of type-II SQWs is quenched by about 4 times with decreasing MAPbL thickness, indicating efficient charge separation. Photodetectors based on type-I and type-II MQW stacked arrangements may have distinct properties, which may translate to a divergence in the device performance. Results as describedherein may highlight the great potential of perovskite MQWs for both light emission and detection.

[0039] MAPbL films were deposited through co-evaporation of lead iodide (Pbl?) and methylammonium iodide (MAI) powders. FIG. 3A shows an optical microscopy image of methylammonium lead iodide (CHsNEFPbls or MAPbL) deposited on indium tin oxide (film thicknesses from left to right: 3 nm, 5 nm, 7 nm, 10 nm and 100 nm). The choice of MAPBL as the perovskite material may be motivated by the larger halide radius in iodine, which leads to a larger exciton Bohr diameter and in turn a larger range of tunability: ~5 nm for M APbh and ~4 nm for methylammonium lead bromide (MAPbBn), although there are no literature values for methylammonium lead chloride (MAPbCL), and the reported values for MAPbl; and MAPbBr? vary significantly. FIG. 3B shows a plot of halide ionic radius (in nanometres or nm) as a function of photoluminescence PL peak shift (in electron volts or eV) illustrating potential bandgap widening upon quantization for methylammonium lead iodide (MAPbh)- based perovskite dependent on the halide ionic radius according to various embodiments. Therefore, ultrathin MAPbh films can achieve a larger extent of quantization compared with Br- or Cl-based perovskite films of the same thickness, potentially unlocking more advantageous optoelectronic properties. Furthermore, MAPbl; may provide access to the red region of the visible spectrum, which is unobtainable with Br / Cl perovskites. MAPbh coevaporation may be alternated with single-source evaporation of either bathocuproine (BCP) or lead phthalocyanine (PbPC) to construct type-I and type-II QW structures, respectively. FIG. 3C shows a schematic illustrating multiple quantum well (MQW) deposition using thermal evaporation cycles according to various embodiments. Compared to solution-processing methods such as spin-coating, thermal evaporation may allow highly precise control of film thickness, allowing the deposition of ultrathin films and MQWs. Evaporation and deposition of each layer may not harm the preceding layer, so this process is inherently additive and can be repeated as desired, unlike spin-coating. Additionally, there may be the possibility of automating the deposition procedure, which may not be possible when spin-coating is involved. Other advantages of thermal evaporation may include film uniformity over a large area, complete and conformal substrate coverage, minimum material waste, and / or amenability to a wide range of substrates, such as transparent conductive oxide-coated glass, flexible metal or plastic foils, and textured silicon Moreover, thermal evaporation may feature a lack ofhazardous solvents, simple upscaling, and ease of integration into existing industrial manufacturing lines.

[0040] FIG. 3D shows schematics and simplified band diagrams of type-I and type-II multiple quantum well (MQW) stacked arrangements constructed of methylammonium lead iodide (MAPblQ with (left) bathocuproine (BCP) and (right) lead phthalocyanine (PbPC), respectively, according to various embodiments. MQWs are classified according to the alignment of their constituent’s bandgaps. In type-I MQWs, the well’s bandgap is contained within the barriers, such that generated electrons and holes are confined in the well. In type-II MQWs, the two bandgaps partially overlap; therefore, charge carriers are segregated into either the well or the barrier. These differing bandgap alignments enable the engineering of charge carrier distribution.

[0041] Several criteria may be applied to look for materials to complement MAPbh in type- I and type-II MQWs. For both types, these criteria are processability with thermal evaporation, suitable valence and conduction energy levels, chemical stability when paired with a perovskite, carrier mobility, and commercial availability. BCP was selected for these reasons and also because its evaporation behaviour is already well -understood owing to its widespread use in optoelectronics research. To select the quantum well material in type-II MQWs, the band gap size and strength of optical absorption may additionally be considered. Inspired by prior research on narrow band gap organic photovoltaics, PbPC may be selected, which fulfils all seven criteria above. 5 nm thick films of BCP and PbPC deposited onto ITO are very smooth, hence suitable for MQW construction. FIG. 3E shows a schematic illustrating the atomic force microscopy (AFM) surface height maps of 5 nm layers of (left) lead phthalocyanine (PbPC) and (right) bathocuproine (BCP) deposited through thermal evaporation onto low roughness indium tin oxide (ITO) substrates according to various embodiments.

[0042] Fine control of thickness may be required to construct the MQWs to obtain the desired extend of quantification. The overall process has been calibrated by profilometry and ellipsometry studies. The thicknesses of the formed films were measured using a profilometer (8400 s) and with ellipsometry (105, 525, 2100 s). FIG. 3F shows a table illustrating the measured methylammonium lead iodide (CFfNHd’bh or MAPbb) film thickness for various deposition times according to various embodiments. FIG. 3G shows a plot of methylammonium lead iodide MAPbh thickness (in nanometres or nm) as deposition time (in seconds or s) illustrating the linear relationship between the measured thickness of evaporatedMAPbh films and deposition time according to various embodiments. The linear relationship between the measured thickness of evaporated MAPbh films and deposition time is in agreement with literature. From the linear fit, a deposition rate of 5.2 nm / minute is extracted, which may then be used to determine the time required to deposit MAPbh films with the required thicknesses. FIG. 3H shows a cross-sectional scanning electron microscope (SEM) image of a type-I multiple quantum well (MQW) stacked arrangement including alternating layers of methylammonium lead iodide (MAPbh) and bathocuproine (BCP) according to various embodiments. The SEM shows 4 layers of BCP (marked by dashed lines) alternating with 3 layers of M APbh.

[0043] Crystalline MAPbh films were formed on ITO, ITO / BCP, and ITO / PbPC down to a thickness of 3 nm, with the (hhO) preferred orientation maintained across all thicknesses and for all subjacent layers, and a nearly stoichiometric composition with a slight Pbh excess (peak at ~12 6°) for the thicker films. FIG. 4A shows (left) a schematic of methyl ammonium lead iodide (MAPbh) layer on low roughness indium tin oxide (ITO)Zglass; (middle) a plot of offset normalized intensity as a function of angle 20 (in degrees or °) illustrating the X-ray diffraction patterns of different thicknesses of methylammonium lead iodide (MAPbh) of the arrangement shown on the left; and (right top) atomic force microscopy (AFM) surface height map of a 5 nm methylammonium lead iodide (MAPbh) layer of the arrangement shown on the left. FIG. 4B shows (left) a schematic of methylammonium lead iodide (M APbh.) layer on bathocuproine (BCP)Zindium tin oxide (ITO)Zglass; (middle) a plot of offset normalized intensity as a function of angle 20 (in degrees or °) illustrating the X-ray diffraction patterns of different thicknesses of methylammonium lead iodide (MAPbh) of the arrangement shown on the left; and (right top) atomic force microscopy (AFM) surface height map of a 5 nm methylammonium lead iodide (MAPbh) layer of the arrangement shown on the left. FIG. 4C shows (left) a schematic of methylammonium lead iodide (MAPbh) layer on lead phthalocyanine (PbPC)Zindium tin oxide (ITO)Zglass; (middle) a plot of offset normalized intensity as a function of angle 20 (in degrees or °) illustrating the X-ray diffraction patterns of different thicknesses of methylammonium lead iodide (MAPbh) of the arrangement shown on the left; and (right top) atomic force microscopy (AFM) surface height map of a 5 nm methylammonium lead iodide (MAPbh) layer of the arrangement shown on the left. The atomic force microscopy (AFM) height maps confirmed a low roughness for all the very thin MAPbh films (5 nm) with values of 1.8 nm for on ITO and ITOZPbPC (FIG. 4A and FIG. 4C), and an even lower of 1.3 nm onITO / BCP (FIG. 4B), suggesting that the BCP smoothed out some of the ITO substrate’s inherent roughness These confinn that the ultrathin MAPbF, films are smooth and continuous, thus being suitable for MQW construction.

[0044] Absorbance spectra of MAPbF films deposited on BCP are shown in FIGS 5A - B, showing a blue-shifted absorption onset in the thinner films. FIG. 5A shows a plot of absorbance as a function of wavelength (in nanometres or nm) illustrating the absorbance spectra of methylammonium lead iodide (MAPbF) layers of various thicknesses deposited on 5 nm bathocuproine (BCP) according to various embodiments. FIG. 5B shows a plot of normalised absorbance as a function of wavelength (in nanometres or nm) illustrating the normalised absorbance spectra of methylammonium lead iodide (MAPbF) layers of various thicknesses deposited on 5 nm bathocuproine (BCP) according to various embodiments

[0045] FIGS. 6A - B show the normalised photoluminescence (PL) spectra and band gaps for type-I and type-II single quantum wells (SQWs) stacked arrangements with different MAPbF, thicknesses. FIG. 6A shows (left) energy band diagram, (middle) a plot of normalised photoluminescence (PL) as a function of energy (in electron volts or eV) illustrating PL spectra of arrangements with different methylammonium lead iodide (MAPbF) thicknesses, and (right) a plot of methylammonium lead iodide ( M APbF, ) band gap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbF) thickness (in nanometres or nm) of type- I methylammonium lead iodide (MAPbF,) / bathocuproine (BCP) (5 nm) single quantum well (SQW) stacked arrangement according to various embodiments. FIG. 6B shows (left) energy band diagram, (middle) a plot of normalised photoluminescence (PL) as a function of energy (in electron volts or eV) illustrating PL spectra of arrangements with different methylammonium lead iodide (MAPbF) thicknesses, and (right) a plot of methylammonium lead iodide (MAPbF) band gap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbF) thickness (in nanometres or nm) of type-II methylammonium lead iodide (MAPbF) / lead phthalocyanine (PbPC) (5 nm) single quantum well (SQW) stacked arrangement according to various embodiments. The emission of type-I and type-II SQWs may be blue-shifted by 116 meV and 84 meV respectively from the 100 nm MAPbF bulk SQW to the 3 nm MAPbF quantized SQW. Both shifts are greater compared to the 64 meV shift exhibited by bare MAPbF films of decreasing thicknesses (as shown in FIG. 6C), with the difference likely due to dielectric confinement. FIG. 6C shows (a) a plot of bandgap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbF) thickness (innanometres or nm) comparing bandgap variations of bare MAPbh and type-I methylammonium lead iodide (MAPbh) / bathocuproine (BCP) single quantum well (SQW) stacked arrangement according to various embodiments; and (b) a plot of bandgap (in electron volts or eV) as a function of methylammonium lead iodide (MAPbh) thickness (in nanometres or nm) comparing bandgap variations of bare MAPbh and type-II methylammonium lead iodide (MAPbl ;) / lead phthalocyanine (PbPC) single quantum well (SQW) stacked arrangement according to various embodiments. In FIG. 6C(a), the dark dots indicate data pertaining to bare MAPbh (i.e., MAPbh. on glass / ITO as shown in the inset), while the light dots indicate data pertaining to type-I methylammonium lead iodide (MAPbh) / bathocuproine (BCP) single quantum well (SQW) stacked arrangement (i.e., BCP / MAPB3I / BCP on glass / ITO stacked arrangement as shown in the inset) In FIG. 6C(b), the dark dots indicate data pertaining to bare MAPbh (i.e., MAPbh on glass / ITO as shown in the inset), while the light dots indicate data pertaining to type-II methylammonium lead iodide (MAPbl ;) / lead phthalocyanine (PbPC) single quantum well (SQW) stacked arrangement (i.e., PbPOMAPBd / PbPC on glass / ITO stacked arrangement as shown in the inset). Each BCP or PbPC layer as illustrated in FIG. 6C is 5 nm thick.

[0046] FIG. 6D shows a plot of integrated photoluminescence (PL) intensity as a function of methylammonium lead iodide (MAPbl;) thickness (in nanometres or nm) illustrating integrated PL intensity normalised to the bulk (50 nm) of each type: methylammonium lead iodide (MAPbl ;), type-I single quantum well (SQW) stacked arrangement, and type-11 single quantum well (SQW) stacked arrangement according to various embodiments. The black dots indicate data related to bare methylammonium lead iodide (MAPbh), the light squares denote data related to type-I SQW stacked arrangement, while the grey hexagons denote data related to type-II SQW stacked arrangement.

[0047] Type-I SQWs achieved an emitted fluorescence almost 50 times stronger than that of a bulk SQW, demonstrating its potential for low-energy light-emitting applications. This may be due to the increased radiative recombination rate and efficiency from the increased exciton binding energy resulting from the quantization effects and spatial confinement from the band alignment. In contrast, the PL emission intensity of the type-II MAPbh SQW is weakened 4-fold as the MAPbh layer is thinned from 100 to 3 nm, due to efficient charge separation between MAPbh and PbPC layers, as illustrated by the band diagram in FIG. 6B.

[0048] A broadening in the PL emission of type-I SQWs as the MAPbh layer gets thinner, while the PL peak width stays roughly constant for the type-II SQWs may also be observed. FIG. 6E shows a plot of photoluminescence (PL) peak Full Width at Half Maximum (FWHM) (in degrees or °) as a function of methylammonium lead iodide (MAPbh) thickness (in nanometres or nm) illustrating PL peak broadening with decreasing MAPbh layer thickness for bare MAPbh (black dots), type-1 single quantum well (SQW) stacked arrangement (light squares), and type-II single quantum well (SQW) stacked arrangement (grey hexagons) according to various embodiments.

[0049] Stronger electron-hole interaction in an exciton may translate to higher rates of radiative recombination, explaining the strong PL emission in type-I SQWs according to various embodiments, especially for the thinnest ones.

[0050] FIG. 6F shows the energy band diagrams of a type-I methylammonium lead iodide (MAPbh) multiple quantum well (MQW) / bathocuproine (BCP) stacked arrangement according to various embodiments, and a type-II methylammonium lead iodide (MAPbI3) multiple quantum well (MQW) / lead phthalocyanine (PbPC) stacked arrangement according to various embodiments.

[0051] To evaluate the photoelectric functionality of MAPbh, MQWs, photodetectors including MQW stacked arrangements on interdigitated tin- doped indium oxide (ITO) substrates were fabricated. FIG. 7 A shows a schematic of a photodetector including the stacked arrangement according to various embodiments. As shown in FIG. 7A, two excitation wavelengths may be used. Bulk 20 nm MAPbh and two-layered type-I MQW (5 nm BCP / 10 nm MAPbh / 5 nm BCP / 10 nm MAPbh / 5 nm BCP) samples were first tested with 525 nm excitation while applying an electric bias to the ITO fingers.

[0052] FIG. 7B shows (left) a plot of photocurrent at 5V (in nano-Amperes or nA) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating photocurrent ( / ph) of type-I multiple quantum well (light squares) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of photocurrent at 5V (in nano-Amperes or nA) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating photocurrent ( / Ph) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of photocurrent at 5V (in nano-Amperes or nA) asa function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating photocurrent ( ph) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.

[0053] FIG. 7C shows (left) a plot of responsivity (in micro-Amperes per Watt or p AW) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating calculated responsivity (R) of type-I multiple quantum well (light squares) and methylammonium lead iodide (MAPbh, ) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of responsivity (in microAmperes per Watt or pA / W) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating calculated responsivity ( / ?) of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of responsivity (in micro-Amperes per Watt or pA / W) as a function of light intensity (in milli- Watts per square centimetre or mW / cm2) illustrating calculated responsivity (R) of type-II multiple quantum well (light hexagons) and methyl ammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.

[0054] FIG. 7D shows (left) a plot of external quantum efficiency EQE (in percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating EQE of type-1 multiple quantum well (light squares) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of external quantum efficiency EQE (in percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating EQE of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments, and (right) a plot of external quantum efficiency EQE (in x 10'4percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating EQE of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.

[0055] FIG. 7E shows (left) a plot of specific detectivity (in * 106Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating specific detectivityof type-I multiple quantum well (light squares) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; (middle) a plot of external specific detectivity (in x io6Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating specific detectivity of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh ) reference (dark dots) photodetectors under 525 nm excitation according to various embodiments; and (right) a plot of specific detectivity (in xio5Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating specific detectivity of type-II multiple quantum well (light hexagons) and methylammonium lead iodide (MAPbh) reference (dark dots) photodetectors under 850 nm excitation according to various embodiments.

[0056] Measurements for FIGS. 7B - E are taken or calculated based on a bias of +5V. The methylammonium lead iodide (MAPbh) reference photodetector contains a 20 nm thick MAPbh film, the type-I multiple quantum well photodetector includes 2 layers of 10 nm-thick MAPbh alternately stacked with 3 layers of 5 nm-thick BCP, while the type-II multiple quantum well photodetector includes 2 layers of 10 nm-thick MAPbh alternately stacked with 3 layers of 5 nm-thick PbPC.

[0057] Values obtained at the maximum incident light intensity are summarized in FIG 7F. FIG. 7F shows a table illustrating the figures of merit of various photodetectors according to various embodiments. The subscript vis refers to visible (525 nm) excitation, with a light intensity of 60 mW / cm2. The subscript IR refers to near-infrared (850 nm) excitation, with a light intensity of 147 mW / cm2. Photocurrent (ZPh) and responsivity R) were extracted at an applied bias of +5 V.

[0058] The type-I MQW may consistently produce slightly higher (up to 5 times) Tph and R compared to the bulk 20 nm MAPbh In contrast, the two-layered type-II MQW (5 nm PbPC / 10 nm MAPbh / 5 nm PbPC / 10 nm MAPbh / 5 nm PbPC) may reveal an over 30 times boost of / Ph (33 x) and R as compared to the bulk photodetector under the same measurement conditions.

[0059] It may be noted that PbPC absorbs weakly and produces a very low current under 525 nm excitation, so only the MAPbh layers are generating a photocurrent when stimulated at that wavelength. FIG. 7G shows plots of absorbance as a function of wavelength (in nanometres or nm) illustrating the absorbance spectra of methylammonium lead iodide (MAPbh) films, lead phthalocyanine (PbPC) / methyl am monium lead iodide (MAPbh) stackedarrangement, lead phthalocyanine (PbPC) / methylammonium lead iodide (MAPbE) / lead phthalocyanine (PbPC) single quantum well stacked arrangement and lead phthalocyanine (PbPC) films in which each MAPbF film or layer is (a) 7 nm, (b) 5 nm and (c) 3 nm thick according to various embodiments Each PbPC layer or film is 5 nm thick

[0060] FIG. 7H shows plots of current (in nano-Amperes or nA) as a function of voltage (in volts or V) illustrating (a) measured output current from the 20 nm methylammonium lead iodide (MAPbh) film under dark and 850 nm infrared light excitation according to various embodiments; and (b) measured output current from the 25 nm lead phthalocyanine (PbPC) film under dark and 525 nm green light excitation according to various embodiments. Both plots in FIG. 7H use the same y-axis range as used in FIG. 7B, and the inset shows zoomed-in y axis ranges. These plots show that the MAPbL layer may not contribute significantly to the current produced by the MQW stacked arrangement under 850 nm light excitation, while the PbPC layer may not contribute significantly to the current produced by the MQW stacked arrangement under 525 nm light excitation.

[0061] This divergence in photodetector performance may highlight the differences in excited state dynamics between type-I and type-II MQWs. The distance between the two ITO contacts in the photodetectors described herein and according to various embodiments is 50 pm, at least an order of magnitude greater than typical exciton and free carrier diffusion lengths in halide perovskite thin films. Furthermore, the large distance between contacts means that the applied electric field inside the detectors as described herein and according to various embodiments may be relatively low even at the maximum bias (105V / m). In comparison, the electric field inside a typical 700 nm thick perovskite solar cell operating at a voltage of 1 V is much higher, at 1.4 x 106V / m. Therefore, the likelihood that excited states would undergo nonradiative recombination before reaching the contacts may be high. In type-I MQW photodetectors, the / Ph increase may be likely due to a combination of the faster radiative recombination (FIG. 6D, FIG. 7D) and the photon recycling it can promote, whose net effect is to reduce the proportion of nonradiative recombination. Meanwhile, in type-II MQW photodetectors, nonradiative recombination may be suppressed by exciton dissociation at the MAPbWPbPC interface and charge carrier segregation between them, as evidenced by the strong PL quenching shown in FIG. 6D. This spatial separation between electrons and holes may allow them to reach their respective contacts without annihilating each other, resulting in higher / ph.

[0062] Due to the presence of the PbPC layer, the type-II MQW photodetectors may also be sensitive to infrared light, expanding the range of their possible applications Their performance under an 850 nm excitation is shown in FIGS. 7B-C, along with the MAPbE-only detector, the values at the maximum incident light intensity is shown in FIG 7F, while the EQE and specific detectivity are shown in FIGS. 7D - E. As expected, the MAPbE-only photodetector may not be responsive under infrared light (FIG. 7H(a)). In contrast, the type-11 MQW photodetectors can work in the near-infrared regime since the optical absorption range of PbPC is complementary to that of MAPbh (FIG. 7G).

[0063] Furthermore, it is found that the type-II MQW photodetectors may work better than reference PbPC-only photodetectors containing the same total PbPC thickness. FIG. 8A shows a plot of photocurrent at 5V (in nano- Amperes or nA) as a function of light intensity (in milliWatts per square centimetre or mW / cm2) illustrating the photocurrents of a type-II methylammonium lead iodide (MAPblj) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments. FIG. 8B shows a plot of responsivity (in micro- Amperes per Watt or pA / W) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the responsivities of a type-II methylammonium lead iodide (MAPbE) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments. FIG. 8C shows a plot of external quantum efficiency EQE (inZI O'4percent or %) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the EQEs of a type-II methylammonium lead iodide (MAPbL) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments. FIG. 8D shows a plot of specific detectivity (in x 105Jones) as a function of light intensity (in milli-Watts per square centimetre or mW / cm2) illustrating the specific detectivities of a type-II methylammonium lead iodide (MAPbE) / lead phthalocyanine (PbPC) multiple quantum well (MQW) stacked arrangement photodetector and a reference phthalocyanine (PbPC) photodetector according to various embodiments. The values in FIGS. 8A - D may be measured or calculated at a bias of +5 V. The PbPC photodetector contains a 25 nm-thick PbPC film, while the type-II MQW contains 4 layers of 5 nm-thick MAPbh alternately stacked with 5 layers of 5 nm-thick PbPC. Under infrared light (850 nm), up to 2.7x increase in photocurrent was observed from the NIR-sensitive type-II MQW photodetector (5 nm PbPC / 5 nm MAPbh / 5 nm PbPC / 5 nm MAPbh / 5 nm PbPC / 5 nm MAPbh / 5 nm PbPC / 5 nm MAPbh / 5 nm PbPC) compared to 25 nm PbPC- only photodetectors. Similar rates of improvements were observed for responsivity and EQE.

[0064] This finding may support the argument that a type-II MQW structure assists exciton dissociation and charge carrier segregation, regardless of whether the excited states are generated in MAPbh or PbPC.

[0065] As shown in FIGS. 7B - D and FIGS. 8 A - D, MQW PDs may produce higher photocurrent than detectors using only MAPbh or only PbPC as the active material, regardless of the excitation light’s wavelength (Visible (Vis) or near-infrared (NIR)). In relation to the results shown in FIGS. 7B - D and FIGS. 8 A - D, two excitation wavelengths are chosen in which only one material is absorbing in each case. Under the green (525 nm) light excitation, PbPC absorbs very little light (FIG. 7G) and the MAPbh thickness was kept the same at 20 nm. The reference MAPbh photodetector contains one 20-nm thick layer while the MQW stacked arrangement photodetectors have two 10-nm thick layers. Similarly, MAPbh may not absorb the NIR 850 nm light as its absorption onset is located at -740 nm. Here, the reference PbPC photodetector contains one 25 nm-thick layer while the MQW PD contains five 5 nm- thick layers. These experimental controls may allow us to conclusively attribute the observed performance improvements shown in FIGS. 7B - D and FIGS. 8 A - D to the nature of the MQW structure used. Further evidence may be provided by FIG. 7H, which shows the reference MAPbh photodetector producing negligible output current under NIR light excitation, and the reference PbPC photodetector photodetector producing negligible output current under visible (Vis) light excitation.

[0066] Thermally evaporated type-I and type-II MAPbh MQWs stacked arrangements incorporating the organic interlayers BCP and PbPC, respectively, have been demonstrated to exhibit exciting optoelectronic properties. In both configurations, MAPbh quantum confinement leads to an ~100 meV band gap widening relative to the bulk band gap, thus minimizing the spatial extent of band banding in the MQW stacked arrangements.

[0067] In type-I MQW stacked arrangements, nearly 50 x emission intensity enhancement may be observed as the MAPbh layer is thinned down into the quantum-confined regime. Furthermore, time-resolved optical spectroscopies showed that the radiative recombination rate in type-I structures may significantly be increased for thinner stacks. These may directly be caused by the confinement of charge carriers in the perovskite wells in type-I MQW stackedarrangements, and may demonstrate their great potential for light-emitting applications. For instance, in the MAPbh / BCP MQW stacked arrangements type-I junctions are formed between each pair of layers. As the perovskite’s band gap is located entirely within the band gap of BCP, both excited electrons and holes may be localized within the perovskite layer. Consequently, the local charge carrier density is increased, and the dominant recombination pathway shifts from the non-radiative Shockley-Read-Hall mechanism to the radiative band- to-band mechanism. The emitted photon from radiative recombination can be reabsorbed to regenerate the excited state, which can then be extracted. As BCP is a wide bandgap material, it may not expand the spectral sensitivity of MAPbh.

[0068] In contrast, type-II MQW stacked arrangements exhibited efficient exciton dissociation and charge separation at the material interfaces, thus substantially improving the performance of the photodetectors. Moreover, such stacked arrangements can also broaden the photodetector’s spectral sensitivity beyond the visible and into the near-infrared region, expanding the range of their possible applications. For instance, in the MAPbh / PbPC MQW stacked arrangement, type- II junctions are formed. As the band gaps of MAPbh and PbPC overlap only partially, excited electrons and holes may be separated into adjacent material layers. This physical separation may prevent them from recombining, and increase or maximize charge extraction. Electrons may go into the MAPbh layer due to the lower conduction band minimum position. Conversely, holes may go into the PbPC layer due to its higher valence band maximum position. This spatial segregation of charge carriers may reduce the likelihood of non-radiative carrier recombination, and increase or maximize the photocurrent output of MQW PDs.

[0069] MAPbh and PbPC may have complementary optical absorbance spectra, with MAPbh absorbing strongly in the ultraviolet UV and visible (Vis) ranges while PbPC absorbs in the near-infrared (NIR) range, with the resulting type-II MQW stacked arrangement exhibiting an absorbance spectrum that covers the UV to NIR range, ideal for applications which would benefit from broadband light detection. In principle, these promising material properties and device performance can also be achieved with other barriers or materials beyond BCP and PbPC, provided that the appropriate band alignment is formed with perovskite.

[0070] Various embodiments may relate to hybrid organic-inorganic iodide-based perovskites type-I and / or type-II MQW stacked arrangements. The fundamental properties ofsuch stacked arrangements have been demonstrated, which may pave the way for applications such as light emitters, lasing, and solar cells.

[0071] Various embodiments may relate to a stacked arrangement including alternating ultrathin layers (e g., < 10 nm) layers of MAPbf perovskite and either BCP or PbPC. Various embodiments may include many heterojunctions, and the photogenerated excited states will need to travel only a short distance to reach the nearest junction. More specifically, because each layer has two interfaces with the other material, the distance that excited states need to traverse is only half of the layer thickness at most (< 5 nm). Consequently, excitons and / or free carriers in either layer have a very good chance of reaching the junctions and be dissociated and spatially separated. This is particularly important for excited states generated in the nonperovskite layer, since the exciton diffusion lengths in organic films are generally less than 10 nm. Accordingly, various embodiments may have advantages over designs including a thick perovskite layer and a thick non-perovskite layer (e g., a thick phthalocyanine layer).

[0072] The use of ultrathin layers may particularly be important for PbPC given its very short excited state diffusion lengths. In contrast, excited states in MAPbh may be able to reach the heterojunction even if the MAPbh layer is relatively thick (hundreds of nm) due to the long excited state diffusion lengths in halide perovskites. However, thinning down the MAPbh layers may also be advantageous. When the MAPbh layer thickness approaches or goes below its Bohr diameter (5.6 nm), the material may become quantised. Compared to thick films, quantum confined MAPbh films may have higher charge carrier densities under optical excitation. The increased charge carrier density may shift the dominant carrier recombination mechanism from the non-radiative Shockley-Read-Hall recombination to radiative recombination, thereby reducing energy losses in a device. FIGS. 6D - E show a 13x amplification in photoluminescence emission intensity from a bulk (50 nm) MAPbh film to a 3 nm-thick one. The rate of emission intensity increase with decreasing MAPbh thickness goes up sharply around the Bohr diameter, showing the significant effect of quantum confinement. This effect may even be stronger in the type-I MQWs, as the carriers are confined to the perovskite layer not just by its thinness (quantum confinement) but also by the presence of the BCP layers (dielectric confinement). As a result, the emission intensity of a type-I MQW with a 3 nm-thick MAPbh may be amplified by about 50x compared to an MQW with a 50-nm thick MAPbh layer. This may signify a strong shift from non-radiative to radiative recombination. In contrast, the emission intensity of atype-IIMQW with a 3 nm-thick MAPbhmay be 4x weaker compared to a type-II MQW with a 50-nm thick M APbb layer. This means sandwiching a 3 nm-thick MAPbb, film with two 5 nm-thick PbPC layers may quench its emission by more than 50x. This large reduction may be a sign of highly efficient exciton dissociation and electron-hole separation at the MAPbL / PbPC heterojunctions. As a result, non-radiative recombination may be suppressed, and electrons and holes can reach their respective contacts without annihilating each other.

[0073] Materials and Methods

[0074] Materials: MAI (99.5%) and PbI2 (99.99%) powder for MAPbb co-evaporation were purchased from Lumtec and TCI, respectively. BCP (99.99%) and PbPC (98%) powder were purchased from Sigma-Aldrich and TCI, respectively. All materials were used without further processing. Interdigitated ITO substrates for photodetectors were purchased from Ossila.

[0075] MQW fabrication: ITO substrates were sequentially cleaned through sonication in a Decon / deionised water solution, deionised water, acetone, and ethanol. After oven drying, the substrates were treated with UV-ozone (for 15 minutes). Then, substrates were transferred into a thermal evaporation chamber. The chamber was closed and evacuated to a base pressure (of 1 x 10'6Torr). MAPbb perovskite layers were deposited by co-evaporating Pbb and MAI powders in individual crucibles The Pbb and MAI source temperatures were maintained at approximately 340-350°C and 130-150°C, respectively (to achieve a perovskite deposition rate of 5.2 nm / min). The total deposition duration was calibrated to achieve accurate film thicknesses. BCP and PbPC layers were deposited in a different thermal evaporation chamber through single-source evaporation of either BCP or PbPC powders, with a deposition rate of 0.1 A / s. In all depositions, substrates were placed on a sample holder rotating at 10 rpm.

[0076] Basic characterization: X-ray diffraction (XRD) was performed with a Bruker D8 Discover Diffractometer with Cu-Karadiation. Absorption spectra were acquired using a UV- Vis-NIR spectrophotometer (Shimadzu, UV-1800) and photoluminescence (PL) spectra were obtained with a spectrofluorophotometer (Horiba, Fluoromax -4C) under 620 nm excitation light. MQW stack was imaged using a field emission scanning electron microscopy (FESEM, JEOL 7600F) with a gun voltage of 5 kV. The film roughness was investigated using an atomic force microscope (AFM) and the height maps were processed using the ARgyle Light software.

[0077] Photodetector measurement: Current-voltage curves of photodetectors were obtained in the voltage range of 0 to +5 V using a probe station fitted with a Keithley 4200SCS analyzer. Two light sources with peak emission wavelengths of 525 and 850 nm (Thorlabs, SOLIS LED) were used. Both sources were controlled with a Thorlabs DC2200 LED driver. All measurements were done without a mask and in ambient air (RH ~ 60%, T = 25°C). Devices were not encapsulated during measurement.

Claims

CLAIMS1. A stacked arrangement comprising: a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers comprising a hybrid organic-inorganic iodine-based metal halide perovskite material; and a plurality of secondary semiconducting material layers comprising a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic- inorganic iodine-based metal halide perovskite layers; wherein each of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers has a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine-based metal halide perovskite material; and wherein each of the plurality of secondary semiconductor material layers has a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer.

2. The stacked arrangement according to claim 1, wherein the stacked arrangement is configured to absorb or emit from visible to infrared light.

3. The stacked arrangement according to claim 1 or claim 2, wherein the secondary semiconducting material has a bandgap different to a bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

4. The stacked arrangement according to claim 3, wherein the bandgap of the secondary semiconducting material has highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) respectively lower and higher than highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

5. The stacked arrangement according to claim 4, wherein the plurality of secondary semiconducting material layers comprise bathocuproine (BCP).

6. The stacked arrangement according to claim 3, wherein the bandgap of the secondary semiconducting material has highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both higher than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

7. The stacked arrangement according to claim 6, wherein the plurality of secondary semiconducting material layers comprise lead phthalocyanine (PbPC).

8. The stacked arrangement according to claim 6 or claim 7, wherein upon irradiation of light onto the stacked arrangement, electrons generated are segregated in the plurality of hybrid organic-inorganic iodine- based metal halide perovskite layers and holes generated are segregated in the plurality of secondary semiconducting material layers, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement9. The stacked arrangement according to claim 3, wherein the bandgap of the secondary semiconducting material has highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both lower than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

10. The stacked arrangement according to claim 9, wherein upon irradiation of light onto the stacked arrangement, holes generated are segregated in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers and electrons generated are segregated in the plurality of secondary semiconducting material layers, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

11. The stacked arrangement according to any one of claims 1 to 10, wherein each of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers is a continuous layer; and wherein each of the plurality of secondary semiconducting material layers is a continuous layer.

12. A method of forming a stacked arrangement, the method comprising: forming a plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers comprising a hybrid organic-inorganic iodine-based metal halide perovskite material; and forming a plurality of secondary semiconducting material layers comprising a secondary semiconducting material, the plurality of secondary semiconducting material layers forming an alternating arrangement with the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers; wherein each of the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers has a thickness in one dimension substantially equal to, or less than a Bohr diameter of the hybrid organic-inorganic iodine-based metal halide perovskite material; and wherein each of the plurality of secondary semiconductor material layers has a thickness in one dimension equal to or less than a thickness required for quantum tunnelling of charge carriers through the respective secondary semiconducting material layer.

13. The method according to claim 12, wherein the plurality of secondary semiconducting material layers and the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers are formed using a vacuum based deposition process14. The method according to claim 13, wherein the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers are formed by co-evaporation of a first source and a second source in the vacuum based deposition process.

15. The method according to any one of claims 12 to 14, wherein the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers comprising the hybrid organic-inorganic iodine-based metal halide perovskite material are formed in a first thermal evaporation chamber; and wherein the plurality of secondary semiconducting material layers comprising the secondary semiconducting material are formed in the first thermal evaporation chamber or in a second thermal evaporation chamber different from the first thermal evaporation chamber.

16. The method according to any one of claims 12 to 15, wherein the secondary semiconducting material has a bandgap different to a bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

17. The method according to claim 16, wherein the bandgap of the secondary semiconducting material has highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) respectively lower and higher than highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

18. The method according to claim 17, wherein the plurality of secondary semiconducting material layers comprise bathocuproine (BCP).

19. The method according to claim 17 or claim 18, wherein upon irradiation of light onto the stacked arrangement, electrons generated and holes generated are in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers, thereby increasing a recombination rate between the electrons and the holes and improving emissive properties of the stacked arrangement.

20. The method according to claim 19, wherein the bandgap of the secondary semiconducting material has highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both higher than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

21. The method according to claim 20, wherein the plurality of secondary semiconducting material layers comprise lead phthalocyanine (PbPC).

22. The method according to claim 20 or claim 21, wherein upon irradiation of light onto the stacked arrangement, electrons generated are segregated in the plurality of hybrid organic-inorganic iodine- based metal halide perovskite layers and holes generated are segregated in the plurality of secondary semiconducting material layers, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

23. The method according to claim 22, wherein the bandgap of the secondary semiconducting material has highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) both lower than respective highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the bandgap of the hybrid organic-inorganic iodine-based metal halide perovskite material.

24. The method according to claim 23, wherein upon irradiation of light onto the stacked arrangement, holes generated are segregated in the plurality of hybrid organic-inorganic iodine-based metal halide perovskite layers and electrons generated are segregated in the plurality of secondary semiconducting material layers, thereby reducing a likelihood of non-radiative carrier recombination and increasing a photocurrent output of the stacked arrangement.

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