HKUST unveils critical nanoscale phenomena for more efficient and stable perovskite solar cells

In a significant advancement for boosting renewable energy generation development, the School of Engineering of the Hong Kong University of Science and Technology (HKUST) has taken the lead in breaking through studies of the nanoscale properties of perovskite solar cells (PSCs). This initiative has resulted in the development of more efficient and durable cells, poised to substantially diminish costs and broaden applications, thereby connecting scientific research with the needs of the business community.

Compared to conventional silicon solar cells, PSCs can potentially attain higher power conversion efficiencies and feature the utilization of lower-cost materials and more sustainable manufacturing processes. Therefore, PSCs have become a cutting-edge research area in energy and sustainability. However, the long-term stability of PSCs when exposed to light, humidity, and thermomechanical stressors remains a major hurdle in commercialization. One key factor causing instability is the inhomogeneous distribution of cations in perovskite thin films, which can trigger an unfavored phase transition that gradually degrades the devices.

A research team led by Prof. ZHOU Yuanyuan, Associate Professor of the Department of Chemical and Biological Engineering and Associate Director of the Energy Institute at HKUST found that the nanoscale groove traps at the perovskite grain’s triple junctions serve as geometric traps that capture cations and retard their interdiffusion towards homogenization. The research team used a rational chemical additive approach known as butylammonium acetate and successfully reduced the depth of these nanoscale groove traps by a factor of three. The resultant cation-homogenized PSCs showed an improved efficiency close to 26%. More importantly, these devices demonstrate advantageous stabilities under various standardized test protocols.

The primary corresponding author of the present study, Prof. Zhou said “Most existing studies focus on the microscopic or macroscopic levels to improve perovskite solar cells. Our team, however, investigated details down to the nanoscale in these PSCs. We used an advanced characterization technique called cathodoluminescence imaging to examine the relation between these nanoscale groove traps and cation distribution. This fundamental approach guided our engineering of these nanogrooves to homogenize the cation distribution and improve the cell performance”.

The findings were published in the top nanoscience journal Nature Nanotechnology, in a paper titled “Nanoscopic Cross-Grain Cation Homogenization in Perovskite Solar Cells”.

HKUST Postdoctoral fellow Dr. HAO Mingwei, the first author of this work, added, “Perovskite is a soft-lattice material. Throughout our experiments, we found notable structural features in perovskite thin films that are remarkably different from those in conventional materials. We are making every effort to elucidate the related mechanisms to promote the commercial viability of perovskite solar cells, pushing forward the development of the renewable energy market with this potential game-changer.”

Prof. Mahshid AHMADI from the University of Tennessee, Knoxville is the co-corresponding author of this work. Other collaborators are from Yale University, Oak Ridge National Laboratory Yonsei University, and Hong Kong Baptist University.

 

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