An international research group has published breakthrough findings demonstrating how the ionic compound caesium bromide (CsBr) can significantly improve the efficiency of crystalline silicon (c-Si) solar cells.
Researchers from the University of Melbourne in Victoria, the University of New South Wales (UNSW), and the Australian National University (ANU) in the Australian Capital Territory (ACT), with scientists based in China, the Netherlands and Germany, found that, by using CsBr as an interlayer, more effective passivating contacts are created.
They demonstrated that a variety of thin, ionic interlayers can create a low-resistance Ohmic contact in solar cells, finding CsBr performed exceptionally well, especially when combined with a passivating layer like titanium oxide (TiOx).
“After annealing at 250 C, the device’s passivation quality and work function were further improved. This optimised structure was used to create a solar cell with an efficiency of over 19% in its as-deposited state, which increased to an impressive 20.5% after annealing,” the researchers said.
The study suggests future improvements could focus on enhancing the passivation quality of the layers and using more reflective materials like silver (Ag) to boost optical performance.
The discovery addresses the challenge in the design of conventional passivating contacts, like amorphous silicon and polysilicon, while being effective in absorbing light reduces efficiency. By contrast, the new CsBr approach allows for greater light absorption, the researchers added.
The team, which includes researchers from Nanchang Hangkong University in China, Eindhoven University of Technology in the Netherlands, and Helmholtz-Zentrum Berlin in Germany, built a laboratory-scale solar cell that integrated the new CsBr layer and achieved the record-breaking efficiency.
“We were able to demonstrate an efficiency of over 20% on a laboratory-scale solar cell that implements the TiOx/CsBr/Al stack as full-area rear-side electron selective contact,” the scientists say.
The research findings can be found in the paper “Electron contact interlayers for low-temperature-processed crystalline silicon solar cells,” published in Progress in Photovoltaics.
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