24.8%-Efficient Planar Perovskite Solar Cells via Ligand-Engineered TiO ₂ Deposition

Abstract

Planar perovskite solar cells (PSCs) have been extensively researched as a promising photovoltaic technology, wherein the electron extraction capability plays a crucial role in the power conversion efficiency (PCE). Here, we proposed a ligand-engineered deposition (LD) strategy based on the coordination ability of ligands (such as tartaric acid) to regulate TiO₂ film and interfacial electron transport. The LD 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 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 fill factor exceeding 0.83 is successfully obtained, which is the highest PCE among the TiO₂-based planar PSCs reported so far. In addition, unencapsulated PSCs can maintain ~95% of their initial efficiency upon exposure to ambient air for 2000 hours.

Keywords: Planar perovskite solar cells, Electron transport layer, TiO2 deposition, Interfacial electron transport, High efficiency, High fill factor