Halogen versus Pseudo-Halogen Induced Perovskite for Planar Heterojunction Solar Cells: Some New Physical Insights

Introducing halogen and pseudohalogen has been one of the effective methods to improve the quality of perovskite film. Planar heterojunction perovskite solar cells based on three lead sources of PbI 2, PbBr 2, and Pb(SCN) 2 were fabricated through a low pressure vapor-assisted solution process. The effect of the lead source on the evolution of the crystal structure, film growth kinetics, electron lifetime, defect density, and photoelectric performance were systematically studied. Although the ultima products in all the three films were CH 3 NH 3 PbI 3, the crystal growth kinetics were absolutely different. These differences indeed strongly affected the films morphologies, defect density, electronic lifetime, and photovoltaic performance of the devices. All the results indicated that the quality of perovskite film based on Pb(SCN) 2 was inferior and the corresponding devices showed obvious deterioration in photovoltaic performance compared to that of PbI 2 and PbBr 2 . Some physical mechanisms have been explained by studying the photoelectric feature of the devices.