Perovskite solar cells are a promising technology that could replace silicon solar cells across various applications, including grid electricity, portable power, and space photovoltaics. They offer higher power conversion efficiencies (PCEs) than commercial silicon cells and have advantages such as low material costs, sustainable manufacturing, and versatility in transparency and color. However, the stability of perovskite devices under light, humidity, and thermomechanical conditions has hindered their commercialization.
To tackle this challenge, Prof. ZHOU Yuanyuan, Associate Professor of the Department of Chemical and Biological Engineering at HKUST, and his research group conducted a study focusing on the microstructure of materials. They discovered numerous surface concavities at the crystalline grains of the perovskite material. These concavities disrupt the structural continuity at the perovskite film interface, acting as a hidden microstructure factor that limits the efficiency and stability of perovskite cells.
The team innovatively removed the grain surface concavities using a surfactant molecule, tridecafluorohexane-1-sulfonic acid potassium, to manage strain evolution and ion diffusion during the formation of perovskite films. Consequently, their perovskite cells showed marked improvements in efficiency retention during standardized thermal cycling, damp heat, and maximum-power-point tracking tests.
"Structure and geometry of individual crystalline grains are the origin of the performance of perovskite semiconductors and solar cells. By unveiling the grain surface concavities, understanding their effects, and leveraging chemical engineering to tailor their geometry, we are pioneering a new way of making perovskite solar cells with efficiency and stability toward their limits," said Prof. Zhou, the corresponding author of this work.
"We were very intrigued by the surface concavities of perovskite grains when we were using atomic force microscopy to examine the structural details of perovskite films. These concavities are usually buried underneath the film bottom and easily be overlooked," he added.
"Microstructure is of vital importance for perovskite solar cells and other optoelectronic devices, and can be more complex than conventional materials owing to the hybrid organic-inorganic characteristics of perovskite materials. Under Prof. Zhou's guidance, we are able to develop various novel characterization and data science approaches to gain insights into perovskite microstructure," said ZHANG Yalan, a PhD student in Prof. Zhou's research group and a co-author of this work.
The team's research, titled "Elimination of Grain Surface Concavities for Improved Perovskite Thin-Film Interfaces," has been published in the prestigious journal Nature Energy. The study was conducted in collaboration with Hong Kong Baptist University and Yale University.
Research Report:Elimination of grain surface concavities for improved perovskite thin-film interfaces
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