Upper coherent interlayers using Cl-SnO2 for improved charge dynamics and efficient inverted perovskite photovoltaics

In recent years, inverted perovskite solar cells (IPVSCs) with a p–i–n structure have attracted widespread attention because of their easy fabrication, cost-effectiveness, suppressed hysteresis, superior operating stability, and low-temperature manufacturing techniques. The inorganic electron transport layers (ETLs) using tin oxide (SnO2) can replace the organic n-type materials to further enhance the device performance and operational stability. The SnO2 nanocrystals were prepared using perchloric acid and dispersed with organic solvents to form the Cl-bonded SnO2 solution. The coupling effect between the Cl-bonded SnO2 film and the Cl-containing perovskite precursor will form a coherent interlayer. This upper coherent interlayer will distinctly suppress charge non-radiative recombination and promote carrier extraction. The high crystallinity of the Cl-bonded SnO2 can also enhance fusion between grains, reduce grain boundaries, and improve the film conductivity. Here, the IPVSCs using all-metal-oxide charge transport materials (CTMs) have achieved the optimal performance with a power conversion efficiency of 23.26% (a VOC of 1.158 V, a JSC of 24.29 mA cm−2, and an FF of 0.827). The adopted all-metal-oxide CTMs can also improve the ambient stability, thermal stability, and light stability. In addition, the dynamic process (charge extraction and recombination) was analyzed in detail. The directly spin-coated Cl-SnO2 ETLs will provide a simple strategy for scalable preparation and commercialization of IPVSCs.