Tailored Semiconducting Heterojunction Interlayer for Efficient Perovskite Solar Cells

In perovskite solar cells (PSCs) with heterogeneous multi-layers, minimizing defects between layers, and aligning energy levels precisely is critical for achieving higher open-circuit voltages and fill factors. A key strategy in achieving these goals involves the introduction of a semiconducting interlayer positioned between the charge-selective layer and the perovskite light absorber, forming a heterojunction with the perovskite layer. This tailored interlayer serves to minimize energy level misalignment and defects. This study explores the notable enhancement in the power conversion efficiency (PCE) of PSCs through a customized heterojunction semiconducting interlayer that can be chemically and physically integrated with the perovskite layer. The interlayer, engineered to ensure fewer defects and harmonized energy levels, was crafted by combining methoxy-phenethylammonium iodide and cyclohexylammonium bromide onto the light-absorbing perovskite thin film. Establishing a heterojunction between the perovskite and the Fermi-level controlled semiconducting interlayer facilitated rapid charge transport and reduced defect density on the perovskite surface. Consequently, an exceptionally high PCE of 26.28% (certified 25.82 per cent) was achieved under standard AM 1.5 global illumination. Furthermore, the encapsulated device exhibits sustained initial efficiency (25.91%) of over 88% following continuous light exposure for 440 h. Impressively, it maintains 100% of its initial efficiency in ambient conditions for over one year (9,000 h). These results underscore the effectiveness of our tailored interlayer design in advancing the domain of high-performance PSCs.