Nanostructure Backreflective Layer for Thin-Film Photovoltaics
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Solution Overview
Problem
Thin-film photovoltaics face limitations in charge transport and light harvesting due to limited absorber thickness, resulting in incomplete light absorption and lower power conversion efficiency.
Innovation Solution
Incorporating a nanostructure backreflective layer, such as metal nanoparticles or nanoporous anodized aluminum oxide, below the photovoltaic device to backscatter incident light, enhancing absorption of angled light while maintaining transparency for normally incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the absorber thickness is increased to improve light harvesting, then light absorption improves, but charge transport deteriorates due to poor charge transport properties of thin-film PV materials
Solution Approach 1:
The patent introduces a backreflective layer that redirects light in the thickness dimension, causing photons to travel laterally through the absorber layer multiple times. This dimensional approach to light management allows increased light harvesting without increasing absorber thickness, thereby maintaining charge transport properties.
Solution Approach 2:
The backreflective layer creates continuous light absorption by reflecting unabsorbed photons back through the absorber layer multiple times. This continuous interaction between light and the photoactive material increases the effective absorption path length without requiring increased material thickness, resolving the contradiction between light harvesting and charge transport.
2Productivity
If a backreflective layer is added to enhance light absorption, then power conversion efficiency improves, but device complexity increases
Solution Approach 1:
The patent employs a porous anodized aluminum oxide layer as the backreflective structure. This porous material provides effective light scattering and reflection while maintaining a relatively simple single-layer structure that can be integrated into existing thin-film PV architectures, minimizing the increase in device complexity.
Solution Approach 2:
The backreflective layer is formed as a composite structure combining anodized aluminum oxide with metallic nanoparticles (such as silver or aluminum). This composite approach enhances the optical properties for light reflection and scattering while maintaining structural simplicity and compatibility with standard PV device fabrication processes.
3Loss of energy
If the absorber thickness is increased to compensate for poor charge transport, then light absorption improves, but manufacturing cost increases due to more material usage
Solution Approach 1:
Instead of increasing absorption by adding more material in the thickness direction, the patent uses the backreflective layer to extend the light path laterally through multiple passes. This dimensional approach to light management achieves enhanced absorption with the same quantity of absorber material, reducing material costs.
Solution Approach 2:
The patent changes the optical parameters of the device by introducing a backreflective layer with specific scattering and reflection properties. This parameter change in the optical path allows the same absorber thickness to achieve higher effective absorption, eliminating the need for increased material quantity.
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
Improves power conversion efficiency by a factor of 1.44 while maintaining up to 70% optical transparency for normally incident light, effectively increasing light harvesting without compromising transparency.
Implementation Method 1
a nanostructure backreflective layer positioned below the substrate such that at least some of the incident light impinging on the photovoltaic device passes through the photovoltaic device and the substrate and is backscattered through the substrate to the photovoltaic device
Implementation Method 2
a photovoltaic device for absorbing incident light having electrodes and one or more layers between the electrodes that includes at least one photoactive layer
Data Source
AI summary
A photoactive device that includes a photovoltaic device having electrodes and at least one photoactive layer between the electrodes. One or more other layers may be included between the electrodes. The device includes a substrate positioned below the photovoltaic device, and a nanostructure backreflective layer positioned below the substrate such that at least some of the incident light impinging on the photovoltaic device passes through the photovoltaic device and the substrate and is backscattered through the substrate to the photovoltaic device.