Effect of plasticizer on safranine-T-dye-based solid-state photo electrochemical cell

Abstract

Effect of plasticizers on electrical and photovoltaic properties of safranine-T-dye-based solid-state photo electrochemical cell (PEC) is studied. Ethylene carbonate (EC) and propylene carbonate (PC) are used as plasticizers. Dark current–voltage characteristic and different photovoltaic parameters such as open-circuit voltage, short-circuit current, and power conversion efficiency are measured. To understand the effect of plasticizers on charge transport process, we analyze the dark current–voltage characteristics to estimate the trap energy. From detail analysis of dark I–V, it has been observed that there is a crossover voltage called transition voltage where the conduction mechanism changes. Above this voltage, the dark current is a space charge limited current (SCLC) in the presence of exponentially distributed traps. Below transition voltage, current is ohmic for the cell without plasticizers and dark current is an SCLC in presence of discrete traps for the cell with plasticizers. From our analysis, it is shown that the transition voltage reduces due to the presence of plasticizers but the characteristic trap energy (ET) is not changed significantly. From photovoltaic measurements, it is observed that in presence of EC and PC power conversion efficiency of the device increase from 7.319 × 10−4% to 14.64 × 10−4% under illumination with polychromatic light of 100 mW/cm2. It is expected that the power conversion efficiency depend on transition voltage. Due to the presence of plasticizers, the barrier potentials of the devices reduce which results lowering of transition voltage. Lowering of it assists the migration of charge carriers and as a result power conversion efficiency enhances.