Perovskite light-emitting diode based on organic interface modification layer

Abstract

The invention is suitable for the field of perovskite photoelectric devices, and provides a perovskite light-emitting diode based on an organic interface modification layer. The structure of the device sequentially comprises an anode ITO substrate, a hole transport layer, an organic interface modification layer, a perovskite layer, an electron transport layer, an electrode modification layer and a metal electrode from bottom to top. And the organic interface modification layer is made of 1, 3-dicarbazole-9-yl benzene molecules. According to the invention, 1, 3-dicarbazole-9-yl benzene molecules with a deep HOMO energy level are introduced between the hole transport layer and the perovskite layer to optimize the carrier transport property and energy level alignment of the hole transport layer, so that effective carrier injection and transport are realized, and exciton quenching at an interface is inhibited. In addition, 1, 3-dicarbazole-9-yl benzene molecules can also interact with a lead octahedron to fill lattice gaps, stabilize a perovskite structure and effectively inhibit generation of defects. Based on the organic interface modification material, the photoelectric property of the perovskite layer is improved, and the device performance is also effectively improved.

Description

Technical Field

[0001] The invention relates to a light-emitting device, in particular to a perovskite light-emitting diode based on an organic interface modification layer. Background Art

[0002] Metal halide perovskites are considered promising materials for next-generation display technologies due to their low cost, solution processability, spectrally tunable properties, and excellent luminescence properties. In just a decade, perovskite light-emitting diodes (PeLEDs) have achieved rapid development, with the external quantum efficiency (EQE) of green PeLEDs exceeding 32% and that of red PeLEDs exceeding 29%. This is comparable to the luminescence efficiency of the most advanced organic light-emitting diodes (OLEDs) and inorganic quantum dot light-emitting diodes (QLEDs). However, the electroluminescent efficiency of blue PeLEDs, which are the basis for full-color displays and lighting, is still significantly lower than that of blue OLEDs and QLEDs. As a prerequisite for achieving full-color display with perovskites, it is crucial to analyze and solve the problem of limited efficiency of blue PeLEDs.

[0003] The main factor limiting the efficiency is the energy loss, which can be attributed to two main aspects of planar devices. The first is the energy loss at the interface and the second is the energy loss within the perovskite. The energy loss at the interface is mainly attributed to the mismatch or imbalance of energy levels, which leads to the accumulation of charge and subsequent exciton annihilation at the interface. Compared with green and red perovskites, blue perovskites show deeper highest occupied molecular orbital (HOMO) energy levels accompanied by a substantial energy level barrier between commonly used hole injection layers, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT∶PSS). This leads to a large number of excitons being released at the bottom interface. The suboptimal efficiency of hole injection leads to considerable energy losses at the interface, which represents an important contributing factor to the observed lower efficiency of blue PeLEDs than that of green and red PeLEDs. Therefore, optimization of the device structure for perovskite light-emitting diodes remains an urgent issue. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to introduce 1,3-dicarbazole-9-ylbenzene molecules as an interface modification layer to improve the hole transport efficiency and charge injection balance. At the same time, the 1,3-dicarbazole-9-ylbenzene molecules can interact with the lead octahedron, adjust the perovskite crystallization and phase distribution, effectively reduce the formation of defects at the interface, thereby significantly reducing the energy loss at the bottom interface and improving the device performance of the perovskite light-emitting diode.

[0005] The purpose of the present invention is to provide a perovskite light-emitting diode based on an organic interface modification layer, which is composed of an ITO anode, a hole transport layer, an organic interface modification layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer, and a metal cathode from bottom to top, wherein the organic interface modification layer is a 1,3-dicarbazole-9-ylbenzene molecule.

[0006] The hole transport layer is at least one of PEDOT:PSS, PVK, CBP and Poly-TPD.

[0007] The electron transport layer is one or more of TPBi, CNT2T, POT2T, TmPyPB and B3PYMPM.

[0008] The electrode modification layer is one of LiF, Liq and CsF.

[0009] The metal cathode electrode is an aluminum electrode or a silver electrode.

[0010] The preparation of the organic interface modification layer comprises the following steps:

[0011] 1,3-dicarbazole-9-ylbenzene (mCP) was dissolved in dichloromethane, and after sufficient stirring and dissolution, an mCP solution with a concentration of 1 to 4 mg / mL was obtained. The mCP solution was evenly spread on the hole transport layer by spin coating, and the spin coating speed was controlled to be 3000 to 6000 rpm. After annealing at 100° C. for 10 minutes, an organic interface modification layer was formed on the hole transport layer.

[0012] The perovskite light-emitting layer has a precursor solution whose components have a molar ratio of CsBr: PbBr2: PbCl2: PEABr: KBr: FABr = 2.8: 1.3: 0.7: 1.0: 0.3: 0.3, wherein the concentration of CsBr is 0.14 mmol / mL, and the solvent is dimethyl sulfoxide.

[0013] The perovskite light-emitting layer precursor solution is spin-coated on the organic interface modification layer, and the spin-coating condition is coating at a rotation speed of 4000 rpm for 60 seconds, and the annealing condition is constant temperature annealing at 70° C. for 7 minutes to form a perovskite light-emitting layer.

[0014] By means of the above scheme, the present invention has at least the following advantages:

[0015] The present invention can optimize the carrier transport and energy level alignment of the hole transport layer by introducing an ultra-thin 1,3-dicarbazole-9-ylbenzene interface layer with a deep HOMO energy level between the hole transport layer and the perovskite layer, thereby achieving effective carrier injection and transport, inhibiting exciton quenching and improving exciton recombination. At the same time, 1,3-dicarbazole-9-ylbenzene can interact with the lead octahedron, fill the lattice gap, stabilize the perovskite structure, and effectively inhibit the generation of defects. The perovskite light-emitting diode of the present invention not only improves the photoelectric performance of the perovskite film, but also effectively improves the device parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram of the mechanism by which mCP improves device charge transport;

[0017] Figure 2 is the XRD pattern of perovskite film;

[0018] Figure 3 is the optical property of the perovskite film;

[0019] Figure 4 This is a performance diagram of perovskite light-emitting diode devices. DETAILED DESCRIPTION

[0020] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0021] Example

[0022] A perovskite light-emitting diode based on an organic interface modification layer, using a device structure of glass / indium tin oxide (ITO) / PEDOT:PSS / mCP / perovskite / TPBi / LiF / Al to construct blue light PeLEDs, wherein ITO is an anode, PEDOT:PSS is a hole transport layer, mCP is an interface modification layer, (Cs / FA / PEA)Pb(Cl / Br)3 perovskite layer is a blue light emitting layer, TPBi is an electron transport layer with a thickness of 45nm, LiF is an electrode modification layer with a thickness of 1.1nm. Al is a metal cathode with a thickness of 80nm.

[0023] The preparation method is as follows:

[0024] (1) After cleaning and drying the ITO transparent conductive glass substrate, the treated ITO substrate is treated with ultraviolet light and ozone, and a hole transport layer PEDOT:PSS is deposited on the treated ITO substrate. Specifically, when depositing the hole transport layer, a portion of the PEDOT:PSS solution is sucked with a syringe, filtered with a filter head, and dripped onto the cleaned ITO transparent conductive glass, and the hole transport layer is formed after drying.

[0025] (2) 1,3-dicarbazole-9-ylbenzene (mCP) was dissolved in dichloromethane, and after sufficient stirring, an mCP solution with a concentration of 2 mg / mL was obtained. The mCP solution was evenly spread on the hole transport layer by spin coating, and the spin coating speed was controlled to be 4000 rpm. After annealing at 100° C. for 10 minutes, an organic interface modification layer was formed on the hole transport layer.

[0026] (3) Prepare the perovskite precursor solution by: -1 )、PbBr2(0.065mmol mL -1 )、PbCl2(0.035mmol mL -1 )、PEABr(0.05mmol mL -1 )、KBr(0.015mmol mL -1 ) and FABr (0.015mmol mL -1 ) concentration, weigh each component, dissolve the above substances in DMSO solvent, place them on a heating table at 35°C and heat with stirring for 4 hours, and filter after complete dissolution to obtain a perovskite precursor solution.

[0027] (4) The ITO transparent conductive glass substrate on which the PEDOT:PSS hole transport layer and the mCP interface modification layer were deposited in step (2) was transferred to a glove box, and then the perovskite precursor solution prepared in step (3) was spin-coated on the upper surface of the hole transport layer at a high speed of 4000 rpm for 60 seconds. After spin coating, the substrate was transferred to a heating table and annealed at 70° C. for 7 minutes to form a perovskite film on the upper surface of the hole transport layer.

[0028] (5) Depositing an electron transport layer, an electrode modification layer and a metal cathode on the perovskite film in step (4) in sequence by high vacuum thermal evaporation to obtain a perovskite light-emitting diode based on a 1,3-dicarbazole-9-ylbenzene organic interface modification layer.

[0029] Comparative Example

[0030] A perovskite light-emitting diode was prepared in the comparative example. The steps of this comparative example and the embodiment are basically the same, the only difference is that the addition of the interface modification layer in step 2 of the embodiment is missing, and the other operating parameters are the same as those of the embodiment. The comparative example prepared a perovskite light-emitting diode without adding a 1,3-dicarbazole-9-ylbenzene organic interface modification layer.

[0031] like Figure 1Shown is a diagram of the mechanism of mCP regulating interfacial charge. Incorporating mCP into the system has the additional benefit of improving energy level alignment and lowering the hole injection barrier. When the sky blue perovskite is in direct contact with PEDOT:PSS with a small work function, a significant energy level barrier is formed between the hole injection layer and the perovskite layer. This barrier causes excitons to accumulate at the PEDOT:PSS / perovskite interface or even jump to the ITO interface. The deep HOMO energy level of the mCP interface modification layer promotes better hole transport, while the high LUMO energy level confines excitons in the perovskite layer, resulting in better radiative recombination, which is also beneficial for promoting device efficiency.

[0032] XRD characterization was used to investigate the effect of mCP interface modification on perovskite crystallization. Figure 2 The X-ray diffraction (XRD) results show that in the presence of mCP, the signal intensity of the perovskite (200) crystal plane is significantly enhanced, indicating that mCP can regulate the crystal growth and crystallization process. The steady-state photoluminescence spectra of the perovskite films grown on the comparative example and example structures are shown in Figure 3 a. It can be observed that the introduction of MCP leads to a significant increase in PL intensity, accompanied by a slight red shift in the emission wavelength from 489 to 490 nm. The significant enhancement in photoluminescence (PL) intensity can be attributed to the significant reduction in non-radiative recombination, which is attributed to the improvement of hole injection and interface defects.

[0033] Figure 3 b shows the transient photoluminescence lifetime spectra (TRPL) of perovskites grown on different structures, compared with the average exciton decay lifetime (τ avg =25.26ns), the lifetime of the perovskite crystal in the embodiment (τ avg =34.72ns) showed a significant enhancement. Figure 3 As can be seen from the PLQY of c, the introduction of the mCP interface modification layer significantly improves the PLQY of the perovskite film, indicating that exciton quenching and defects at the interface are effectively alleviated. This phenomenon may also help reduce carrier loss. The reduction in defect state density is mainly attributed to the fact that mCP can effectively interact with the lead octahedron and inhibit the generation of defects. Figure 3 It can be seen from the steady-state absorption spectrum of d that the low n phase (n=2) of the perovskite film of the embodiment is significantly reduced, and the n=3 phase is slightly enhanced, indicating that the mCP interface modification layer can adjust the distribution of the quasi-two-dimensional phase.

[0034] Figure 4 The performance of the device with and without the mCP interface modification layer is shown. Figure 4 As shown in a, compared with the comparative device without mCP, the on-state voltage (V on) is significantly reduced. This reduction can be attributed to the reduction of the hole injection barrier induced by mCP. The results show that the maximum brightness of the embodiment device with mCP interface modification layer is 1460 cd m -2 The maximum external quantum efficiency is 18.42%, which is significantly higher than the 1040 cd m of the comparative device without mCP. -2 and 13.72%( Figure 4 a, 4b). It is obvious that incorporating mCP as an interface modification layer significantly improves the efficiency of the device, which can be attributed to the reduction of energy losses at the interface.

[0035] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A perovskite light-emitting diode based on an organic interface modification layer, characterized in that: From bottom to top, it is composed of an ITO anode, a hole transport layer, an organic interface modification layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer and a metal cathode, wherein the organic interface modification layer material is a 1,3-dicarbazole-9-ylbenzene molecule; The hole transport layer is at least one of PEDOT:PSS, PVK, CBP and Poly-TPD; The electron transport layer is one or more of TPBi, CNT2T, POT2T, TmPyPB and B3PYMPM; The electrode modification layer is one of LiF, Liq and CsF; The metal cathode electrode is an aluminum electrode or a silver electrode; The preparation of the organic interface modification layer comprises the following steps: Dissolve 1,3-dicarbazole-9-ylbenzene (mCP) in dichloromethane, stir and dissolve to obtain a mCP solution with a concentration of 1 to 4 mg / mL, evenly spread the mCP solution on the hole transport layer by spin coating, control the spin coating speed to be 3000 to 6000 rpm, anneal at 100 °C for 10 minutes, and form an organic interface modification layer on the hole transport layer; The perovskite light-emitting layer has a precursor solution whose component ratios are CsBr∶PbBr2∶PbCl2∶PEABr∶KBr∶FABr=2.8∶1.3∶0.7∶1.0∶0.3∶0.3, wherein the CsBr concentration is 0.14 mmol / mL, and the solvent is dimethyl sulfoxide; The perovskite light-emitting layer precursor solution is spin-coated on the organic interface modification layer, and the spin-coating condition is coating at a rotation speed of 4000 rpm for 60 s, and the annealing condition is constant temperature annealing at 70° C. for 7 min to form a perovskite light-emitting layer.

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