Perovskite semiconductor-engineered cascaded molecular energy levels in naturally-sensitized photoanodes

Abstract Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alternatives to enhance photoabsorption, electron excitation/injection, but voltage loss remains a challenge. Here, we focus on understanding the cascading of energy levels in perovskite semiconductor cosensitized naturally-sensitized photoanodes to leverage forward charge transport addressing the voltage loss arising from ITO/TiO2 heterojunction's built-in potential. The β -carotene-sensitized TiO2 photoanode modified with methylammonium lead iodide (MAPbI3) co-sensitizer causes an upward shifting in TiO2 Fermi level (EF). This phenomenon is predominantly attributed to increased initially injected electrons due to low MAPbI3 bandgap and high visible-light absorption. Enhanced charge separation and injection mechanisms at the TiO2/MAPbI3 interface increase the effective density-of-states (DOS >2.46 × 1021 cm−3) in the TiO2 conduction band (CB) and hence decrease its work function to 4.82 eV. The decrease in TiO2 work function suppressed CB bending at ITO/TiO2 heterojunction, which minimized the photoinduced electrostatic potential barrier up to 13.1%. The reduced Schottky barrier ( φ S B H β -carotene-sensitized solar cell.