NaCl-passivated and Na+-doped tin oxide electron transport layers enable highly efficient planar perovskite solar cells. (November 2021) - Dong, Lika
Abstract: Tin oxide (SnO2 )-based electron transport layers (ETLs) are used to make flexible perovskite solar cells (PSCs) because of their low-temperature properties. However, when pure SnO2 is used, the poor interface formed between the SnO2 ETL and the perovskite layer is detrimental to the efficiency of the PSCs. In this work, we report the synthesis and characterisation of a SnO2 –NaCl composite ETL. Na + and Cl − at the ETL/perovskite interface passivate the ETL/perovskite contact and suppress nonradiative recombination centres. Meanwhile, Na + diffuses from the ETL to the perovskite film, passivating its grain boundaries. The outstanding capability of Na + to increase the grain size and consequently improve the charge dynamics and increase the power conversion efficiency was also verified. PSCs with a SnO2 –NaCl ETL exhibited an open-circuit voltage of 1.11 V, which was higher than the reference (1.08 V) for lower band gap perovskite absorbers, and achieved a power conversion efficiency of 18.56% with negligible hysteresis. Highlights: A simple strategy of doping a SnO2 solution with Na + and Cl − to increase the power conversion efficiency of perovskite solar cells. Na + and Cl − in the SnO2 solution simultaneously passivate the defects at the electron transport layer/perovskite interface and at the grain boundaries of the perovskite film. Na + on the surface of SnO2 film diffuses into the perovskite layer, leading to an increase in grain size of the perovskite. Our work demonstrates the importance of the electron transport layer and interfacial properties of perovskite solar cells and offers an elegant and versatile approach for improving the performance of perovskite solar cells.