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

Planar perovskite solar cells (PSCs) have been extensively re-searched as a promising photovoltaic technology, wherein the elec-tron extraction and transfer play a crucial role in the power conver-sion 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. Further-more, 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 success-fully 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.

Automated summary

In this research, a ligand-engineered deposition strategy was proposed to improve the performance of planar perovskite solar cells. By using tartaric acid as the ligand, particle aggregation was effectively inhibited, and the interfacial contact impedance was reduced while the electron extraction was enhanced. The obtained PCE of 24.8% with a fill factor exceeding 0.83 is the highest reported among TiO2-based planar PSCs so far.