Oligoether chain was incorporated to construct self-assembling molecules, which can not only enable good coverage and optimized buried interface properties but also assist high-quality and ordered perovskite growth as well as regulate top energetics of perovskite. Consequently, a remarkably high efficiency of 25.50% was realized in perovskite solar cells along with enhanced long-term stability.

Abstract

Self-assembling molecules (SAMs) are widely used as interfacial layers to optimize the surface properties of nickel oxides (NiO_x) in inverted perovskite solar cells (PSCs). However, less attention is paid to the effect of SAMs on the regulation of perovskite growth and energetics. Here, based on the donor-acceptor molecular backbone, an oligoether chain is introduced with different chain lengths to endow two novel SAMs, namely, EPA and MEPA, with good capability of bottom-up regulation of perovskite formation and energetics. Compared to the model SAM MPA, EPA and MEPA can render NiO_x with better coverage and conductivity. Moreover, the oligoether chain-containing SAMs are able to assist the formation of perovskite film with ordered growth, high crystallization, and importantly well-matched energy level alignment at the top surface, especially for MEPA. Consequently, a remarkably high efficiency of 25.50% is realized for NiO_x/MEPA-based PSCs along with good device stability, which can maintain 90% of the initial efficiency under ISOS-L-1 conditions over 1260 h.