Constructing bottom-up n-p perovskite homojunctions for enhanced performance of electron transport layer-free solar cells.

We constructed the high-quality perovskite films with bottom-up n-p homojunctions via a modified sequential two-step deposition technique, which optimized the energy level alignment between the perovskite layer and the adjacent contacts for promoting charge separation and extraction, as well as suppressing non-radiative recombination. The resultant n-p homojunction-based electron transport layer-free perovskite solar cells achieved improved efficiency, which was ∼13% higher than that of the control counterpart.