Suppressed Degradation and Enhanced Performance of CsPbI3 Perovskite Quantum Dot Solar Cells via Engineering of Electron Transport Layers

CsPbI 3 perovskite quantum dots (CsPbI 3 -PQDs) have recently come into focus as a light-harvesting material that can act as a platform through which to combine the material advantages of both perovskites and QDs. However, the low cubic-phase stability of CsPbI 3 -PQDs in ambient conditions has been recognized as a factor that inhibits device stability. TiO 2 nanoparticles are the most regularly used materials as an electron transport layer (ETL) in CsPbI 3 -PQD photovoltaics; however, we found that TiO 2 can facilitate the cubic-phase degradation of CsPbI 3 -PQDs due to its vigorous photocatalytic activity. To address these issues, we have developed chloride-passivated SnO 2 QDs ( [email protected] 2 QDs), which have low photocatalytic activity and few surface traps, to suppress the cubic-phase degradation of CsPbI 3 -PQDs. Given these advantages, the CsPbI 3 -PQD solar cells based on [email protected] 2 ETLs show significantly improved device operational stability (under conditions of 50% relative humidity and 1-sun illumination), compared to those based on TiO 2 ETLs. In addition, the [email protected] 2 -based devices showed improved open circuit voltage and photocurrent density, resulting in enhanced power conversion efficiency (PCE) up to 14.5% compared to that of TiO 2 -based control devices (PCE of 13.8%).