Researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences, in collaboration with international partners, have engineered a thin two-dimensional perovskite phase at the buried interface of three-dimensional (3D) perovskite solar cells (PSCs) to boost device performance and operational stability.
The method, published in Nature Energy on February 6, improves the crystallization quality of perovskite films and reduces defect concentrations at the buried interfaces by more than 90 percent (a tenfold decrease).
A primary bottleneck limiting the photovoltaic performance and stability of PSCs is the presence of numerous defects on the devices' top and bottom surfaces. While incorporating long-chain ammonium salts into the bulk perovskite can form 2D perovskite phases both in the bulk and at the buried interfaces of the film, fabricating 2D structures exclusively at buried interfaces has been a challenge.
To address this problem, the research team sequentially grafted thioglycolic acid (TGA) and oleylamine (OAm) onto the surface of tin dioxide (SnO 2 ) nanoparticles, yielding the modified material SnO 2 -TGA-OAm. Strong chemical bonding between TGA and OAm ensures that cation exchange with formamidinium iodide (FAI) occurs only during the thermal annealing of perovskite films, enabling the spontaneous formation of a 2D/3D perovskite heterostructure solely at the film's bottom interface.
The researchers employed the novel SnO 2 -TGA-OAm nanoparticles as a multifunctional electron-transporting layer. PSCs fabricated with this layer achieved impressive power conversion efficiencies (PCEs) of 26.19% for small-area devices (0.09 cm 2 ), 23.44% for a module with an aperture area of 21.54 cm 2 (certified at 22.68%), and 22.22% for a large-area module with an aperture area of 64.80 cm 2 . "These values rank among the highest efficiencies reported to date for small-sized PSCs and modules based on 2D/3D perovskite heterojunctions," noted Dr. ZHAO Qiangqiang, first author of the study.
"This in situ solid-state ligand-exchange strategy could be easily scalable from lab to factory production while delivering enhanced operational stability," added Prof. PANG Shuping, a corresponding author of the study. "It brings the commercialization of PSCs significantly closer to realization."
This work paves the way for fabricating 2D/3D heterojunctions at the buried interface of perovskite absorber layers and is expected to accelerate the commercial application of perovskite photovoltaic technology.
Nature Energy