Nanofiber-modified Electron Transport Layer for Perovskite Solar Cells

Tin dioxide (SnO2) is widely used in perovskite solar cell (PSC) as an electron transport material due to its high transmittance, high electron mobility, good UV stability, and low-temperature processing. However, SnO2 electron transport layer prepared from commercial colloidal solution still faces some challenges such as easy agglomeration, defects, and energy level mismatch, limiting its performance and stability. This study improved the quality of SnO2 films by introducing a polymer chitin nanofiber (1,2-dibenzoyloxyphenylchitin, DC) into the SnO2 precursor solution, and systematically studied the effect of DC on the precursor solution, film and device performance. Experimental results showed that DC additive could effectively inhibit the agglomeration of SnO2 nanoparticles, ensuring a more homogeneous dispersion in the precursor solution. The improved SnO2 films had smaller roughness and could be better wetted by perovskite solution, which is beneficial to closer contact with the perovskite layer. Simultaneously, the oxygen vacancy defects in the SnO2 films were effectively passivated, and the proportion of defects was reduced to 30%, further improving the quality of the films. Based on the improved energy level matching between the SnO2 electron transport layer and the perovskite layer, the carrier extraction and transport performance was optimized. The performance of DC-modified PSC was significantly improved, and the photoelectric conversion efficiency of the optimal device reached 19.11%. This work not only overcomes the agglomeration problem of the SnO2 electron transport layer during the preparation process, but also provides theoretical guidance and method for improving the performance of perovskite solar cells.