Solvent Engineering of SnO 2 ETL for Enhanced Performance of Carbon-Based CsPbIBr 2 PSCs

This study thoroughly investigates the effects of different solvent engineering strategies on the structure and properties of SnO2 electron transport layers (ETLs) and evaluates their performance-enhancing effects on carbon-based all-inorganic CsPbIBr2 perovskite solar cells (PSCs). By comparing the SnO2 ETLs prepared with ethanol (ET-SnO2) and isopropanol (IPA-SnO2) solvents and constructing corresponding CsPbIBr2 PSCs devices, we comprehensively analysed the structure, morphology, wettability, light transmittance and electronic transport properties of the SnO2 ETLs using characterisation methods such as XRD, SEM, contact angle measurement, transmission spectroscopy, steady-state fluorescence spectroscopy and electrochemical impedance spectroscopy. Combined with the J-V characteristics of the device, we revealed the mechanism of the effect of solvent engineering on the performance of PSCs. The results showed that IPA-SnO2 exhibited better performance with lower contact angle and higher compactness, which is conducive to electron transport and reduces interfacial defects. IPA-SnO2 also promoted the growth of CsPbIBr2 crystals, forming larger and denser crystal structures and reducing pinhole defects. In addition, IPA-SnO2 improves the light transmittance of the FTO substrate and the light absorption of the CsPbIBr2 film, thereby increasing the light trapping efficiency. Finally, the IPA-SnO2-based PSCs achieved a PCE of 5.95%, an improvement of 25% compared to ET-SnO2, demonstrating good application prospects. This study provides an important theoretical and experimental basis for optimising the preparation process of SnO2 ETL and improving the performance of carbon-based CsPbIBr2 PSCs.