24.8%-efficient planar perovskite solar cells via ligand-engineered TiO2 deposition

Abstract

<h2>Summary</h2> Planar perovskite solar cells (PSCs) have been extensively researched as a promising photovoltaic technology, wherein the electron extraction and transfer play a crucial role in the power conversion efficiency (PCE). Here, we proposed a ligand-engineered deposition strategy based on the coordination ability of ligands (e.g., tartaric acid) to regulate TiO₂ film and interfacial structure. This strategy can effectively inhibit particle aggregation of TiO₂ film through the steric hindrance of assembled ligands. Furthermore, the decreased interfacial contact impedance and enhanced electron extraction are achieved between TiO₂ and perovskite, due to the smooth topography and cross-linked structure formed by tartaric acid that bonds with Ti and Pb atoms. Accordingly, an impressive PCE of 24.8% with a fill factor exceeding 0.83 is successfully obtained, which is the highest PCE among TiO₂-based planar PSCs reported so far. In addition, unencapsulated PSCs can maintain ∼95% of initial efficiency upon exposure to ambient air for 2,000 h.