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SnO 2 electron transport layers (ETLs) had an essential role in the n-i-p structure of perovskite solar cells. Improving the quality of the electron transport layer and enhancing interfacial contacts were key factors in the fabrication of high-performance perovskite solar cells. Therefore, a non-ionic polymeric polyacrylamide (PAM) modified SnO 2 colloidal solution with improved clustering of SnO 2 nanoparticles was presented to form a uniform and dense SnO 2 electron transport layer. The results demonstrated that no pinhole pores were found at the interface where the PAM-modified electron transport layer and the light absorbing layer came into contact, a structure that facilitated carrier transport and reduced carrier recombination at the interface location. Further beneficial effects were revealed by femtosecond Fs-TA measurements and trap of states (tDOS) analysis, where the carrier lifetime τ 2 decreased from 306.7 ps to 137.8 ps and the trap density of states of the film also decreased significantly. Correspondingly, the SnO 2 -PAM device exhibited an optimum efficiency of 21.61 %. Fantastic device stability was obtained due to the interaction of excellent contact at the SnO 2 /FAPbI 3 interface, and 85 % of the initial efficiency was maintained when placed in air for 1000 h for photo-aging tests, thereby improving the stability of FAPbI 3 grains. This method of improving the quality of tin oxide colloidal solutions provided a novel and simple way to prepare efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]