Linearly Tailored Work Function of Orthorhombic CsSnI3 Perovskites

Currently, the green tin halide perovskites are emerging as one of alternatives to their toxic lead halide counterparts. However, the recognized big problem hindering their application in photovoltaic devices is their inferior open-circuit voltage, which could be effectively addressed by tuning work function (Phi). Herein, we propose a strategy for tailoring the Phi of gamma-CsSnI3 via surface passivation with phenyl-ethylammonium (PEA(+)) and its halogen derivatives (XPEA(+)) by first-principles calculations. The ID of gamma-CsSnI3 is tightly correlated with the surface dipole, while the contributions from surface structure relaxation and charge exchange are negligible. Accordingly, the Phi can be linearly aligned with a slope of -1.435 and Adj. R-2 of 0.995 from 1.74 to 5.28 eV as a function of surface dipole and ligand layer coverage. Consequently, the reduced Phi causes a downward band bending to facilitate electron transfer with enhanced V-OC, underscoring their potential in efficient environmentally friendly solar cells.

Automated summary

By using surface passivation, the work function of γ-CsSnI3 can be tailored, leading to improved performance of photovoltaic devices.