Assessment of Interface Passivation in AgBiS2 Q-dot Sensitized Solar Cell on the carrier transport and recombination

Abstract

Silver bismuth sulfide has been discovered to be an appropriate light-harvesting material but the carrier transport restrictions and trap-assisted recombination in Q-dot AgBiS₂ limit the device efficiency. To address inherent charge carrier transport restrictions and trap-assisted recombination in q-dot AgBiS₂, this work studied the effect of interface passivation of AgBiS₂ Q-dot by a thin-nanostructured ZnS layer on carrier transport and recombination.The charge-transfer and carrier recombination processes investigated by open-circuit voltage decay curves and electrochemical impedance spectroscopy indicate the decrease in inherent trap-assisted Shockley-Read-Hall (SRH) recombination in bare AgBiS₂ due to the passivation of AgBiS₂ by ZnS while an increase in the charge recombination resistance and improvement in carrier lifetime resulting in enhanced solar cell performance. A very thin ZnS passivation layer on AgBiS₂ also boosts the light absorption, resulting in a red shift in the light absorption peak. The formation of AgBiS₂ and ZnS was confirmed by XRD, EDS, and TEM analysis and the explicit role of the ZnS passivation layer on the electron transport layer and the light harvesting AgBiS₂ Q-dots was investigated. Using a polysulfide electrolyte and optimal ZnS layers on TiO₂ and AgBiS₂ nanostructures in the FTO/m-TiO₂/ZnS(1)/AgBiS₂/ZnS(2) electrode design enhanced the efficiency and the passivation can also be implemented for a solid-hole transport material.