Highly efficient and freely soluble titanium sub-oxide powder as interfacial functional material for versatile photovoltaic cells

Abstract

Metal suboxides (MOs) are among the most attractive interfacial materials owing to their outstanding functionality and excellent electrical and optical properties. However, the limitations of solution processability and ambient stability of the precursor hinder their widespread application. In this study, we developed a novel methodology for the solidification of sol–gel-derived MO-based organic complexes without affecting the properties of the MO products. By controlling the polarity of a conventional sol–gel derived titanium suboxide solution (STO) with organic functional side groups, we can easily obtain a nearly monodispersed solid-state precursor of STO (PTO) with excellent solubility in alcohols. PTO demonstrates ideal optical and electrical properties as an electron transport layer (ETL) with a significantly enhanced stability due to the elimination of the reactive residue. Owing to the optical, electrical, and excellent film-forming properties of PTO, organic and perovskite solar cells with PTO exhibit drastically improved performances and stability. Thus, a PTO-based ETL was successfully fabricated on various active layers, including those prepared from organic and perovskite materials, demonstrating the universality of PTO.