Built-in field manipulation through a perovskite homojunction for efficient monolithic perovskite/silicon tandem solar cells

Abstract

Perovskite-silicon tandem solar cells offer a solution to exceed the Shockley–Queisser limit of their respective single-junction counterparts and significantly reduce the levelized cost of energy (LCOE) of photovoltaic systems. While thick perovskite film is imperative in this tandem configuration to ensure complete coverage on the textured silicon surface, it gives rise to great challenges for carrier transport and extraction. Herein, we designed a layer of mesoporous Al2O3 at the buried interface to establish a perovskite homojunction and mitigate the inherent adverse electric field in the perovskite film. Results showed that the Al2O3 layer evidently interacted with the organic cations of perovskite materials, effectively suppressing the spontaneous ion migration during crystallization. Thus, it altered the semiconductor type of the perovskite film at the buried interface from n-type to p-type, enabling the formation of perovskite homojunction and rendering it suitable for inverted perovskite solar cells (PSCs) by enhancing the built-in electric field. As a result, an outstanding power conversion efficiency (PCE) of 22.16 % is attained for a single junction 1.67 eV PSCs. Furthermore, we successfully crafted efficient monolithic perovskite/silicon tandem solar cells with this strategy, achieving an impressive PCE of 29.04 %. This study highlighted the critical importance of regulating local ion distribution in perovskite films and enhancing the built-in electric field for tandem configurations, which also provided a fresh perspective on the role of mesoporous Al2O3 in PSCs.