<p>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 characterization 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 experimental basis for optimizing the preparation process of SnO₂ ETL and improving the performance of carbon-based CsPbIBr₂ PSCs.</p> Graphical Abstract <p></p>