Elucidating the effect of shunt losses on the performance of mesoporous perovskite solar cells

Mesoporous perovskite solar cells (MPSCs) suffer from various types of charge carrier losses, where shunt losses usually dominate. Herein, we perform a systematic study to investigate the impact of such losses on the photovoltaic performance of methylammonium lead iodide (MAPbI₃)-based MPSCs. The shunt losses in the MPSCs are attributed to the leakage current and the non-geminated recombination losses. We also demonstrate that these losses can be reduced by the incorporation of appropriate thickness of compact titanium oxide (c-TiO₂) interlayer between FTO and mesoporous TiO₂ (m-TiO₂). As a result, MPSCs exhibit higher open-circuit voltage (V_OC) of 1.05 V, short-circuit current density (J_SC) of 23.27 mA cm⁻², and the power conversion efficiency (PCE) of 17.69% under one-sun illumination conditions. The improved device performance was attributed to (i) the efficient blocking of holes, (ii) the decrease of leakage current, and (iii) the suppression of the non-geminated recombination losses in the cells. The effect of the c-TiO₂ layer thickness on the series resistance (R_S), shunt resistance (R_Sh), and the non-geminated recombination were also discussed in detail.