Improving the performance of planar perovskite solar cell using NH4Cl treatment of SnO2 as electron transport layer

Here in this research, a modified interface between the electron transport layer (ETL) and the perovskite layer in a perovskite solar cell (PSC) is provided by adding the ammonium chloride (NH4Cl) to the tin oxide (SnO2) as the modified ETL of a planar structure as follows: fluorine-doped tin oxide (FTO)/NH4Cl-SnO2/Mixed cation perovskite/Copper indium disulfide (CIS)/Gold (Au). The effects of NH4Cl on ETL are investigated in different amounts from 0.003 to 0.02 M and the best results were obtained in the amount of 0.013 M. The best NH4Cl-SnO2 ETL could increase the power conversion efficiency (PCE) of fabricated planar PSC by 16.79% with open-circuit voltage (Voc) of 1.15 V and negligible hysteresis behavior, while the device with the pristine-SnO2 ETL showed the PCE of 14% with 1.04 V as the Voc. Moreover, the modified ETL made a better energy level alignment at the ETL/perovskite interface than the unmodified one, resulting in improvement of Voc and carrier extraction simultaneously. The electrochemical impedance spectroscopy (EIS) measurement indicated that the surface modification of SnO2 with NH4Cl increases the carrier extraction and decreases the recombination centers in the device. Finally, the stability of initial PCE in devices was examined after 30 days without encapsulation which expressed an improvement of 42% in the case of NH4Cl-SnO2 ETL (78%) as compared to the sample with pristine-SnO2 ETL (55%).