Self-Assembled Multilayer Photon Upconversion for Solar Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current solar cell technologies face efficiency limitations due to the inability to effectively harness sub-bandgap light, leading to potential energy losses, and existing photon upconversion methods are inefficient, especially when integrated with metal oxide surfaces.
Innovation Solution
A self-assembled multilayer structure comprising an acceptor molecule covalently bonded to a metal oxide surface, a linking coordinating metal ion, and a sensitizer molecule, which facilitates photon upconversion through triplet-triplet annihilation, ensuring close proximity and efficient energy transfer between the sensitizer and acceptor molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inorganic solids (lanthanide-doped crystals) are used for photon upconversion, then upconversion efficiency can be achieved under high intensity irradiation, but the system becomes unsuitable for applications where high intensity light is destructive or unavailable, and requires concentrator technology
Solution Approach 1:
The patent transitions from inorganic solid upconversion requiring high intensity irradiation to molecular upconversion using organic sensitizer and acceptor molecules that operate at low light intensities. This parameter change in the upconversion mechanism enables applicability to biological systems and solar energy conversion where high intensity light is either destructive or unavailable
Solution Approach 2:
The patent introduces molecular intermediaries (sensitizer and acceptor molecules) that mediate the upconversion process at metal oxide surfaces. These molecular mediators enable efficient energy transfer and upconversion under low intensity light conditions, making the system suitable for solar energy conversion and biological applications
2Adaptability or versatility
If molecular upconversion is used with sensitizer and acceptor molecules, then the system can operate under low intensity light, but the integration with metal oxide surfaces is inefficient
Solution Approach 1:
The patent segments the upconversion system into distinct functional components: metal oxide surface, acceptor molecules, and sensitizer molecules. This segmentation allows each component to be optimized for its specific function while maintaining efficient interfacial interactions, resolving the inefficiency of molecular upconversion integration with metal oxide surfaces
Solution Approach 2:
The patent creates a composite material system combining metal oxide surfaces with organic sensitizer and acceptor molecules. This composite structure integrates the advantages of inorganic surfaces (stability, surface area) with organic molecules (low intensity light operation, tunable energy levels), achieving both efficient upconversion and suitability for solar energy conversion
3Device complexity
If standard single-junction solar cells are used, then the device structure is simple, but the maximum theoretical efficiency is limited to approximately 34% due to transmission of low energy sub-bandgap light
Solution Approach 1:
The patent applies preliminary action by using photon upconversion to convert sub-bandgap photons to higher energy photons before they reach the solar cell's active layer. This pre-conversion of low energy light enables the solar cell to utilize previously wasted spectral regions, increasing overall efficiency without fundamentally changing the solar cell structure
Solution Approach 2:
The patent converts the harmful effect of sub-bandgap light transmission (energy loss) into a benefit by using upconversion to transform these low energy photons into higher energy photons that can be effectively utilized by the solar cell, thereby converting waste into useful energy
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances photon upconversion efficiency, enabling direct photocurrent generation and potentially increasing solar cell efficiencies beyond conventional limits by effectively utilizing sub-bandgap light, as demonstrated by the bilayer and trilayer films on metal oxide surfaces.
Implementation Method 1
Photon upconversion is a photophysical process where the energy from two or more lower frequency photons are combined to generate a single, higher frequency photon
Implementation Method 2
The alternative strategy, molecular upconversion, requires a pair of molecules that are often labeled as a sensitizer (or donor) and an emitter (or acceptor) molecule
Implementation Method 3
lower energy light is absorbed by the sensitizer molecule to generate a singlet excited state that quickly undergoes intersystem crossing to produce a triplet excited state
Implementation Method 4
the sensitizer-acceptor pair will undergo energy transfer to generate an acceptor molecule in the triplet excited state
Implementation Method 5
an acceptor molecule covalently bonded to a metal oxide surface
Implementation Method 6
a linking coordinating metal ion bonded to the acceptor molecule
Data Source
AI summary
Transmission of low energy light is one of the primary loss mechanisms of a single junction solar cell. Molecular photon upconversion via triplet-triplet annihilation (TTA-UC)—combining two or more low energy photons to generate a higher energy excited state—is an intriguing strategy to surpass this limit. The present disclosure is directed to self-assembled multilayers, e.g., bi- or trilayers, on metal oxide surfaces as a strategy to facilitate TTA-UC emission and demonstrate direct charge separation of the upconverted state. A three-fold enhancement in transient photocurrent is achieved at light intensities as low as two equivalent suns. The multilayer structure comprises a substrate comprising a metal oxide surface and a bulk region, and a self-assembled bilayer film, the bilayer film comprising: (a) an acceptor molecule covalently bonded to the metal oxide surface; (b) a linking metal ion bonded to the acceptor molecule; and (c) one or more sensitizer molecule(s) bonded to the linking coordinating metal ion.