The Role of SnO₂ Processing on Ionic Distribution in Double-Cation-Double Halide Perovskites

Moving toward a future of efficient, accessible, andless carbon-reliantenergy devices has been at the forefront of energy research innovationsfor the past 30 years. Metal-halide perovskite (MHP) thin films havegained significant attention due to their flexibility of device applicationsand tunable capabilities for improving power conversion efficiency.Serving as a gateway to optimize device performance, considerationmust be given to chemical synthesis processing techniques. Therefore,how does common substrate processing techniques influence the behaviorof MHP phenomena such as ion migration and strain? Here, we demonstratehow a hybrid approach of chemical bath deposition (CBD) and nanoparticleSnO(2) substrate processing significantly improves the performanceof (FAPbI(3))(0.97)(MAPbBr(3))(0.03) by reducing micro-strain in the SnO2 lattice, allowingdistribution of K+ from K-Cl treatment of substrates topassivate defects formed at the interface and produce higher currentin light and dark environments. X-ray diffraction reveals differencesin lattice strain behavior with respect to SnO2 substrateprocessing methods. Through use of conductive atomic force microscopy(c-AFM), conductivity is measured spatially with MHP morphology, showinghigher generation of current in both light and dark conditions forfilms with hybrid processing. Additionally, time-of-flight secondaryionization mass spectrometry (ToF-SIMS) observed the distributionof K+ at the perovskite/SnO2 interface, indicatingK(+) passivation of defects to improve the power conversionefficiency (PCE) and device stability. We show how understanding therole of ion distribution at the SnO2 and perovskite interfacecan help reduce the creating of defects and promote a more efficientMHP device.