High Fidelity Nano-Structured Bulk Heterojunction for Solar Cells
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Solution Overview
Problem
Current photovoltaic devices face limitations in efficiency due to the short lifetime of excitons and the lack of control over nano-scale morphology, leading to charge trapping and restricted device size, making it challenging to achieve effective light harvesting and exciton dissociation in large-area solar cells.
Innovation Solution
A high fidelity bulk heterojunction photovoltaic device is fabricated using a predetermined array of nano-scale structures with uniform dimensions and orientations, allowing for efficient exciton dissociation and charge separation, and enabling the production of large-area devices by molding techniques with low-surface energy polymeric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photovoltaic devices are used, then device fabrication is simpler, but efficiency is limited due to short exciton lifetime and lack of nano-scale morphology control
Solution Approach 1:
The photovoltaic device is segmented into distinct functional regions with predetermined nano-scale structures, including a first region with first nano-scale structures and a second region with second nano-scale structures. This segmentation allows each region to be optimized for specific functions (exciton generation, transport, dissociation) while maintaining overall device efficiency and controlling nano-scale morphology through structured design rather than random distribution.
Solution Approach 2:
Different regions of the photovoltaic device are assigned different nano-scale structures and material compositions tailored to local functional requirements. The first region contains structures optimized for light absorption and exciton generation, while the second region contains structures optimized for charge separation and electron transport. This local quality approach ensures that each area contributes maximally to its specific function, improving overall exciton dissociation efficiency while maintaining precise nano-scale control.
2Reliability
If bulk heterojunction is used for exciton dissociation, then light harvesting is improved, but charge trapping occurs due to random distribution of materials
Solution Approach 1:
The bulk heterojunction is segmented into distinct regions with controlled material distribution. Rather than relying on random mixing of electron donor and acceptor materials, the device incorporates a first region with specific nano-scale structures for light harvesting and a second region with different structures for charge separation. This segmentation maintains the benefits of bulk heterojunction for light absorption while eliminating charge trapping caused by random material distribution.
Solution Approach 2:
Electron donor and acceptor materials are distributed non-uniformly according to local functional requirements. The first region contains material compositions optimized for light harvesting and exciton generation, while the second region contains compositions optimized for charge separation. This local quality approach ensures efficient light harvesting in the first region while preventing charge trapping in the second region, achieving both goals simultaneously.
3Area of stationary object
If device size is increased for larger footprint, then energy production capacity is improved, but exciton diffusion distance becomes excessive leading to recombination
Solution Approach 1:
Large-area photovoltaic devices are divided into multiple functional regions, each with predetermined nano-scale structures spaced at optimized intervals. The first region handles light absorption and exciton generation, while the second region handles charge separation. This segmentation allows the device to maintain large footprint for high energy production capacity while ensuring that no exciton must diffuse beyond its maximum diffusion length to reach a charge separation interface, preventing recombination losses.
Solution Approach 2:
The device architecture transitions from a two-dimensional planar structure to a three-dimensional hierarchical structure with vertically stacked functional regions and laterally distributed nano-scale structures. This dimensional change allows the device to achieve large footprint area while maintaining short exciton diffusion paths through the vertical stacking of functional layers, resolving the contradiction between device size and charge separation efficiency.
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
The approach enhances the efficiency of solar cells by ensuring effective exciton dissociation and charge separation, enabling the production of photovoltaic devices with larger footprints while maintaining high fidelity and uniformity in nano-scale structures.
Implementation Method 1
solar cells generate electricity by converting light energy into electricity through excitons
Implementation Method 2
When light is absorbed an electron is promoted from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) forming an exciton. In a PV device, this process must be followed by exciton dissociation to form an electron and a hole
Data Source
AI summary
A photovoltaic device includes an electron accepting material and an electron donating material. One of the electron accepting or donating materials is configured and dimensioned as a first component of a bulk heterojunction with a predetermined array of first structures, each first structure is substantially equivalent in three dimensional shape, has a substantially equivalent cross-sectional dimension, and where each first structure of the array of first structures has a substantially equivalent orientation with respect to adjacent first structures of the predetermined array forming a substantially uniform array.