Above 800 mV Open-Circuit Voltage in Solid-State Photovoltaic Devices Using Phosphonium Cation-Based Solid Ionic Conductors

Here, we report phosphonium-based two solid ionic conductors (SICs), namely, triphenylphosphonium methyl iodide (TPPMeI) and triphenylphosphonium iodide (TPPHI), prepared via simple protocol at room temperature and were used as an electrolyte for solid-state photovoltaic devices (ss-PVDs) with open-circuit voltage (Voc) exceeding 800 mV. Here, for the first time, detailed electrochemical investigations with theoretical aspects of phosphonium electrolytes were conducted, where PVDs prepared from these SICs, TPPMeI, showed the highest power conversion efficiency (PCE) of 4.08% with a Voc of 810 mV. However, this performance was further improved up to the PCE of 6.71% with 824 mV of Voc in the presence of additives like LiI and tert-butyl pyridine. This work leads to find the best alternative of liquid and quaternary ammonium ion-based electrolytes that suffers from problems like lower Voc (<800 mV) and stability, leakage, etc.