TiOxNy Interlayer for Multijunction Solar Cells With Lower Reflection
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Solution Overview
Problem
Existing multi-junction photovoltaic devices face challenges with interconnect layers, such as high reflection losses and the presence of shunt paths, which are exacerbated by the use of indium-tin oxide (ITO) layers. Additionally, the deposition processes used for these layers, like plasma enhanced chemical vapor deposition (PECVD), are costly, complex, and have low deposition rates.
Innovation Solution
The introduction of a metal oxynitride layer, specifically titanium oxynitride (TiOxNy), between the perovskite and silicon sub-cells in multi-junction photovoltaic devices. This layer is deposited using physical vapor deposition methods like sputtering, which offers higher deposition rates and simpler, less expensive equipment compared to PECVD. The TiOxNy layer is designed to reduce reflectivity losses and enhance electrical interconnection between the sub-cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ITO layers are used as interconnect layers, then electrical conductivity is improved, but reflection losses increase and shunt paths form
Solution Approach 1:
The patent introduces an intermediate layer comprising a metal oxide (such as titanium oxide, tin oxide, or zinc oxide) positioned between the perovskite top cell and the ITO interconnect layer. This intermediate layer acts as a mediator that reduces reflection losses at the interface while maintaining the electrical conductivity function of the ITO layer, thereby resolving the contradiction between electrical conductivity and reflection losses
Solution Approach 2:
The patent creates a composite structure by combining the metal oxide intermediate layer with the ITO interconnect layer. This composite material approach allows the system to simultaneously exhibit the low-reflection properties of the metal oxide and the high electrical conductivity of the ITO layer, effectively addressing both requirements
2Manufacturing precision
If PECVD process is used for deposition, then film quality is improved, but deposition rate decreases and equipment cost increases
Solution Approach 1:
The patent replaces the plasma-enhanced chemical vapor deposition (PECVD) process with a simpler physical vapor deposition or sputtering process. This substitution reduces equipment complexity and increases deposition rate while still achieving films with sufficient quality for the application, trading off some film quality for significant gains in productivity and reduced equipment cost
3Manufacturing precision
If PECVD process is used for deposition, then film quality is improved, but equipment complexity and cost increase
Solution Approach 1:
The patent replaces the complex plasma-enhanced chemical vapor deposition (PECVD) equipment with simpler physical vapor deposition or sputtering equipment. This substitution eliminates the need for complex plasma generation and control systems while still producing functional films, thereby reducing equipment complexity and cost
4Reliability
If ITO layers are used as interconnect layers, then electrical conductivity is improved, but shunt paths are formed through perovskite absorbers
Solution Approach 1:
The patent introduces an intermediate metal oxide layer as a mediator between the perovskite top cell and the ITO interconnect layer. This intermediate layer prevents direct contact between the ITO and perovskite, thereby eliminating the formation of shunt paths while still allowing electrical conductivity to be maintained through the composite structure
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 use of a TiOxNy interlayer significantly reduces reflection losses and improves the electrical interconnection between sub-cells, leading to enhanced power conversion efficiency and reduced manufacturing costs. The results show a slight increase in short-circuit current density and open circuit voltage, while maintaining a high fill factor, thus improving the overall performance of the multi-junction photovoltaic devices.
Implementation Method 1
the use of a sub-stoichiometric nanocrystalline silicon oxide (nc-SiOx) layer, located on top of an amorphous silicon i-layer and below an ITO layer, which forms the contact to the p-layer of the top cell, is proposed by L. Mazzarella et al., Advanced Energy Materials 2019, 9(14), 1803241. To reduce the reflection between the perovskite top cell and the silicon bottom cell
Implementation Method 2
the deposition processes used for these layers, like plasma enhanced chemical vapor deposition (PECVD), are costly, complex, and have low deposition rates. The TiOxNy layer is deposited using physical vapor deposition methods like sputtering
Data Source
AI summary
A multi-junction photovoltaic device comprising a layer of metal oxynitride between a first sub-cell and a second sub-cell is disclosed, the first sub-cell having a layer comprising a perovskite light absorber material. In addition, a method of manufacturing said multi junction photovoltaic device is disclosed. The metal oxynitride is preferably titanium oxynitride. Advantageously, the device may be produced in a simple, fast, consistent and inexpensive manner, whilst the properties of the titanium oxynitride layer may be tuned to avoid the occurrence of local shunt paths and to reduce reflection losses.