Self-repairing tin-based perovskite solar cells using 2,4-dichlorophenylhydrazine hydrochloride as dopant

Low efficiency and poor stability are considered as the dominant factors that hinder the further development of tin-based perovskite solar cells due to the easy oxidation of the divalent tin ions (Sn²⁺). Aiming at solving the issues, 2,4-dichlorophenylhydrazine hydrochloride (DPHH) is doped into the FASnI₃ perovskite film to inhibit the oxidation of Sn²⁺ to the tetravalent tin ions (Sn⁴⁺). The molecular structure of DPHH contains reductive hydrazine group and hydrophobic phenyl group, which can effectively protect the ions of Sn²⁺, prevent the further degradation of FASnI₃ film. Further analysis of the surface morphology and crystal structure reveal that DPHH can effectively improve the crystallinity and grain size of the FASnI₃ perovskite film, which is beneficial for increasing the resistance of charge recombination. More importantly, the devices exhibit superior self-repairing property in device lifetime testing. It’s confirmed that the phenylhydrazine ion (Ph⁺) in DHPP can partially reduce Sn⁴⁺ formed by oxidation to Sn²⁺, so as to partially repair the defects of the film and enhance the performance. Therefore, the modified devices exhibit enhanced device performance, including enhanced power conversion efficiency as well as longer liftetime.