Reducing the interfacial voltage loss in tin halides perovskite solar cells

Abstract

Tremendous attention has been given to tin halide perovskite solar cells (TPSCs) due to the lower toxicity and similar electronic configuration compared with the lead perovskites. Nevertheless, on account of the intrinsic low bandgap, high defect density and surface/interface non-radiative recombination, the open-circuit voltage loss (Vloss) of TPSCs is comparatively large in all semiconductor solar cells. Herein, a hydrophobic bulky molecule of 3-(trifluoromethyl) phenethylamine hydroiodide (CF3PEAI) was utilized to passivate the lead-free perovskite surface by post-deposition treatment. The Vloss of the corresponding PSC devices was significantly reduced to afford a high open-circuit voltage (Voc) up to 0.73 V with a power conversion efficiency (PCE) of 10.35% in conjunction with the broadly utilized (6,6)-Phenyl C61 butyric acid methyl ester (PC61BM). Additionally, the CF3PEAI interlayer expressively suppressed the interfacial non-radiative recombination accompanying with extending photoexcited carrier lifetime. The formation of oriented 2D Sn-based perovskite could also facilitate the vertical charge-carrier transportation and improve the efficiency of Sn-based PSCs. The density of defect states and the amount of mid-gap states required to be filled were both dramatically reduced. Meanwhile, the surface reconstruction can effectively relax the tensile surface strain with the phenethyl ammonium iodide ligands. Therefore, this surface passivation strategy contributes to the development of high-quality lead-free perovskite film with low internal defects and residual stress.