An international research team has conducted an extensive review of all back-contact (BC) solar cell types in an effort to accelerate their commercial development.
The scientists grouped the cell types based on designs, charge transport mechanisms, fabrication strategies, and emerging challenges and created two main categories – interdigitated back-contact (IBC) and quasi-interdigitated back-contact (QIBC) devices.
They emphasized that the back contact design, compared to conventional sandwich structures, can reduce the cell’s effective defect tolerance, with the quality of electrode connections playing a key role in preventing this from happening.
“In back-contact perovskite solar cells, in which charge extraction also relies on buried selective contacts, device performance hinges not only on band alignment but also on interface quality and defect management,” they further explained. “Applying passivation layers on the perovskite layer could further improve both the operational stability and efficiency of the devices by enhancing defect tolerance and suppressing nonradiative recombination at defect sites.”
The researchers also summarized the advantages and disadvantages of the traditional silicon-based sandwich-type IBC and QIBC configurations and stressed that both IBC and QIBC perovskite cells require an additional insulating layer, which addresses some of the challenges faced by typical IBC silicon solar cell designs.
“This insulating layer between the electrodes reduces the risk of shunting and allows for easier control of the electrode gap, enabling more reliable fabrication,” the group stated. “The QIBC architecture also supports layer-by-layer deposition of charge-selective layers and corresponding electrodes, and it is compatible with a variety of patterning techniques.”
The research also highlighted the current limitations BC perovskite cells to overcome to reach commercial maturity. These include expensive photolithography methods used for their production, poor materials selectivity, unbalanced charge extraction at the interface between the perovskite absorber and the electron transport layer, and charge diffusion length limiting factors in lead halide perovskite materials.
The academics also outlined a strategy to optimize nanophotonic structure and light capture in BC perovskite cells. They suggested improving ETL optimization through electron transport, using antireflective coatings (ARCs), and optimizing perovskite film properties, for example.
“To further advance the back-contact technology in PSCs, it is highly required to focus on low-cost patterning techniques, in addition to the development of a clear picture of charge carrier transport dynamics, ion migration, and photon recycling effects on the overall device performance,” they added. “Alternative methods that permit low-cost, high-resolution, and high-throughput back-contact electrode fabrication must be developed.”
Their review can be found in the paper “Revolutionizing light capture: a comprehensive review of back-contact perovskite solar cell architectures,” published in Materials Today. The research team was formed by scientists from Japan’s Kanazawa University, the University of California and the Islamic University of Madinah in Saudi Arabia.
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