Passivating defects via 4-cyanobenzenaminium iodide enables 22.44% efficiency perovskite solar cells. (1st May 2022)

• Record Type: Journal Article
• Authors: Liang, Lusheng; Xiong, Qiu; Zhang, Zilong; Yu, Yaming; Gao, Peng
• Is Part Of: Electrochimica acta. Volume 413(2022)
• Publication Date: 2022-05-01
• Subjects: 4-cyanobenzenaminium iodide -- Organic halide salts -- Cyano group -- Defect passivation -- Perovskite solar cells; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2022.140172
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: A new organic halide salt with cyano group, 4-cyanobenzenaminium iodide (CNBAI), is developed to passivate the defects of perovskite. CNBAI can passivate the defects of perovskite in multi-role. For the first time, experimentally demonstrated cyano group can simultaneously interact with Pb 2+ and form N … I halogen bond. The CNBAI-passivated devices achieved a best PCE of 22.4% with little hysteresis and good long-term stability. Abstract: Defects can easily form at the surfaces and grain boundaries of solution-processed organic-inorganic halide perovskites films, leading to undesired non-radiative recombination and ion migration in the device. Consequently, this limits the performance of perovskite solar cells (PSCs). Herein, a new organic ammonium halide salt with cyano (-CN) functional group, 4-cyanobenzenaminium iodide (CNBAI), was developed to passivate the defects in the bulk of perovskite films. It was found that the CNBAI can improve the film morphology of the perovskite layer and passivate the various types of defects in the perovskite. On the one hand, the -CN group could bind with the under-coordinated Pb 2+ and form intermolecular halogen bonds with the iodide atom in perovskite, as illustrated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy measurements. On the other hand, CNBAI could fill the iodide vacancy with its own iodide ions. For the first time, we demonstrate experimentally that the -CN group can simultaneously interact with Pb 2+ and form CN … I halogen bond in the perovskite. In addition, the introduced CNBAI improved energy alignment between the perovskite and adjacent charge transport layers. Finally, the PSCs fabricated with CNBAI-based perovskite films achieved the best PCE of 22.4% with negligible hysteresis and displayed good long-term stability. Abstract : Image, graphical abstract .