Experimental and Simulated Analysis of Polymer Hole Transport Layers and the Electrical and Optical Effects on Perovskite Solar Cells

This study presents a systematic analysis of the impact of polymer hole transport layers (HTLs) in inverted MAPbI₃ perovskite solar cells (PSCs). Devices were fully fabricated under regular atmospheric conditions (≈40% humidity) and low temperature (100 °C) by using Field's Metal (FM) as an alternative top electrode. The widely known π-conjugated polymers P3HT, PTB7-Th, PBDB-T, and MEH-PPV were used as HTLs, and all of them show suitable energy alignment to MAPbI₃, offering good moisture stability, solution processability, low cost, and attractiveness for large area and flexible PSCs. Morphological and structural characterization of MAPbI₃ via AFM, SEM, and XRD revealed consistent crystallinity, with MEH-PPV promoting a slightly larger grain size and surface modification. Current density-voltage (<i>J</i>-<i>V</i>) characteristics showed that MEH-PPV-based PSCs achieved an enhanced open-circuit voltage (<i>V</i>_oc ≈1.07 V) and fill factor (FF ≈75%), along with reduced hysteresis, while impedance spectroscopy (IS) confirmed enhanced charge extraction and lower ohmic losses. Simulations of external quantum efficiency (EQE) revealed that MEH-PPV reduces front-interface optical losses by ≈32% and charge recombination losses at the front and rear MAPbI₃ interfaces by ≈33% and ≈75%, respectively, in comparison to P3HT.