Enhancing the Performance of Perovskite Solar Cells by Introducing 4-(Trifluoromethyl)-1H-imidazole Passivation Agents

Abstract

Defects in perovskite films are one of the main factors that affect the efficiency and stability of halide perovskite solar cells (PSCs). Uncoordinated ions (such as Pb2+, I−) act as trap states, causing the undesirable non-radiative recombination of photogenerated carriers. The formation of Lewis acid–base adducts in perovskite directly involves the crystallization process, which can effectively passivate defects. In this work, 4-(trifluoromethyl)-1H-imidazole (THI) was introduced into the perovskite precursor solution as a passivation agent. THI is a typical amphoteric compound that exhibits a strong Lewis base property due to its lone pair electrons. It coordinates with Lewis acid Pb2+, leading to the reduction in defect density and increase in crystallinity of perovskite films. Finally, the power conversion efficiency (PCE) of PSC increased from 16.49% to 18.97% due to the simultaneous enhancement of open-circuit voltage (VOC), short circuit current density (JSC) and fill factor (FF). After 30 days of storage, the PCE of the 0.16 THI PSC was maintained at 61.9% of its initial value, which was 44.3% for the control device. The working mechanism of THI was investigated. This work provides an attractive alternative method to passivate the defects in perovskite.

Modulating Crystallization and Defect Passivation by Butyrolactone Molecule for Perovskite Solar Cells

“…Among them, additive engineering is mostly used because it can trigger different effects on perovskite films, from nucleation to the final ripening process [ 17 , 18 , 19 ]. For example, several inert large molecules, supramolecules, and polymers have been explored to target the undesired defects by adding them to the perovskite precursor solutions [ 1 , 20 , 21 , 22 , 23 ]. The defects at the grain boundaries can be finely passivated by forming hydrogen bonds or coordination bonds with the additive, and a moisture barrier can be built to improve the stability.…”