Charge Accumulation Effects in Hole-Transporting Materials on Current–Voltage Performance in Solar Cells

High Resolution Image Download MS PowerPoint Slide Hole-transporting material (HTM) layer often plays a crucial buffer role in efficient solar cells and is normally known to serve as a preferential extractor of photogenerated holes from the adjacent absorber film. Here, the CuI film is controllably prepared and the current density–voltage ( J – V ) properties in the Sb 2 S 3 solar cells with CuI and spiro-OMeTAD as the HTMs that possess remarkably different hole mobilities (μ h ) are comparatively investigated. While two solar cells exhibit a comparable efficiency of 4–5%, the CuI-based solar cell of a much lower μ h in the HTM layer exhibits an abnormal J – V property, quite different from the spiro-OMeTAD-based one. The μ h -defined contribution of the HTM layer to photocurrent generation is found to cause the abnormal J – V property and the principles behind the μ h -dependent overall device performance get elucidated. An intensity-dependent hole accumulation barrier model is proposed to understand the big discrepancy between the short-circuit current density values measured under AM 1.5G illumination and expected from external quantum efficiency, and a two-source equivalent circuit model is developed to understand the μ h -defined contribution of the HTM layer to a high photocurrent generation, offering mechanistic insights into the importance of the charge mobility in the HTM layer to solar cell performance.