Highest-Efficiency Flexible Perovskite Solar Module by Interface Engineering for Efficient Charge-Transfer

The electron-transport layer (ETL) plays an important role in improving the performance of flexible perovskite solar cells (F-PSCs). Herein, a room-temperature-processed SnO2:OH ETL is demonstrated, that exhibits reduced defect density, in particular lower oxygen vacancy concentration, with better energy band alignment and more wettable surface for quality perovskite deposition. More importantly, an efficient electron-transfer channel is produced between the ETL and the perovskite layer due to the formation of hydrogen bonds at the interface, resulting in enhanced electron extraction from the perovskite. As a result, the efficiency of a large-area (36.50 cm(2)) flexible perovskite solar module based on MAPbI(3) is increased to as high as 18.71%; this is thought to be the highest reported PCE value for flexible perovskite solar modules to date. In addition, it exhibits high durability while maintaining over 83% of its initial PCE after flexing test cycles. Further, F-PSCs with SnO2:OH show remarkably long-term stability, owing to a high quality of the perovskite film and a strong coupling between the SnO2:OH and perovskite layer caused by hydrogen bonds, which successfully inhibits moisture permeation.

Automated summary

A room-temperature-processed SnO2:OH electron-transport layer with reduced defect density and better energy band alignment has been demonstrated for flexible perovskite solar cells. The formation of hydrogen bonds at the interface produces an efficient electron-transfer channel, leading to enhanced electron extraction from the perovskite. With this ETL, a large-area flexible perovskite solar module reaches a PCE value of 18.71%, the highest reported so far for flexible perovskite solar modules. The long-term stability is also greatly improved due to the high quality perovskite film and the strong coupling between SnO2:OH and perovskite layer caused by hydrogen bonds, which effectively inhibits moisture permeation.