SnO Passivation and Enhanced Perovskite Charge Extraction with a Benzylamine Hydrochloric Interlayer.

Perovskite solar cells (PSCs) have gained much attention because of their expressive power conversion efficiency (PCE) of up to 25.5%. A good contact and a well-aligned energy level at the buried interfaces between electron transport layers (ETLs) and perovskite films play an essential role in promoting charge-carrier collection and suppressing nonradiative recombination. Currently, low-temperature-processed SnO thin films are widely used as the ETLs to achieve efficient and stable planar PSCs. However, fabricating proper SnO/perovskite interfaces with a good contact and a well-aligned energy level is necessary but implies a great challenge. Herein, we modify the SnO ETL using benzylamine hydrochloride (BH), which is expected to facilitate the energy level alignment and to enhance perovskite crystallization. Moreover, the BH interlayer is found to effectively reduce the trap-state density and thereby improve the charge-carrier extraction between the ETL and the perovskite layer. Consequently, the PSC with BH modification yields a higher PCE, a lower hysteresis, and better stability than the device without a BH interlayer. This study highlights the key role of molecule modification of ETLs in designing efficient and stable PSCs.