image: Schematic diagram of liquid Ga nanodroplet-templated heteroepitaxial growth of MAPbI₃ crystals
Credit: ©Science China Press
A research team led by Professor Qingju Liu from Yunnan University has developed an innovative strategy to significantly improve the performance of printable mesoscopic perovskite solar cells (p-MPSCs) by using liquid gallium nanodroplets as a heteroepitaxial template. The study was published in Science Bulletin.
Printable mesoscopic perovskite solar cells are considered a promising low-cost and stable alternative to traditional photovoltaics. However, their power conversion efficiency has historically trailed behind that of planar perovskite devices, primarily due to constrained crystal growth within the mesoporous oxide scaffold, which results in small grains and high charge recombination.
The team introduced liquid Ga nanodroplets into the mesoporous TiO₂ layer. Upon exposure to air, these nanodroplets form an ultrathin Ga₂O₃ shell that acts as an epitaxial template. Through atomic-resolution imaging and density functional theory (DFT) calculations, the researchers demonstrated that the (110) plane of MAPbI₃ grows epitaxially on the Ga₂O₃ (400) surface with an ultralow lattice mismatch of just 0.32%. This guided growth enables the formation of large, highly oriented perovskite crystals exceeding 200 nm within the confined mesopores—a significant advancement for this solar cell architecture.
The champion device achieved a power conversion efficiency of 20.2% (0.10 cm²) with negligible hysteresis. Furthermore, the cell exhibited exceptional operational stability, retaining 97% of its initial efficiency after 3000 hours of continuous operation under high humidity and temperature (85% RH, 55°C).
This liquid metal templating method provides a generalizable strategy for controlling crystal growth in confined spaces and shows great potential for the scalable printing of high-performance, stable perovskite solar cells.
The study was funded by the National Key Research and Development Program of China, National Natural Science Foundation of China, the Key Research and Development Program of Yunnan Province, the Young and Middle-Aged Academic and Technical Leaders Reserve Talent Project in Yunnan Province. the Scientific and Technological Project of Yunnan Precious Metals Laboratory, and the Caiyun Postdoctoral Innovation Project in Yunnan Province. The authors also acknowledged the technical support from various centers at Yunnan University.