Beach-Chair-Shaped Energy Band Alignment for High-Performance β-CsPbI3 Solar Cells

Summary CsPbI3 perovskite has drawn worldwide attention because of its thermal stability and outstanding photovoltaic performance. However, further improvement of CsPbI3 device performance is hindered by significant energy losses via charge-carrier recombination at the CsPbI3/transport layer interface and moisture sensitivity. Here, a beach-chair-shaped band structure is designed to introduce energy level gradients at both sides of the perovskite layer to steer optimal energy band alignment and heterojunction interface passivation in β-CsPbI3 perovskite solar cells (PSCs), resulting in suppressed interfacial recombination, enhanced charge extraction, and more robust stability. As a result, champion solar cell efficiency is increased to as much as 17.12%, one of the highest in reported CsPbI3 PSCs, and the Voc of 1.15 V is among the highest reported values. Furthermore, bare PSCs without encapsulation retain 90.4% of their initial cell efficiency after being stored for 1 month under ambient conditions.