Researchers from the Chinese Academy of Sciences (CAS), KTH Royal Institute of Technology, Xián Polytechnic University, Northwestern Polytechnical University, Qingdao University of Science and Technology and King Abdullah University of Science and Technology (KAUST) have designed a 2D perovskite layer, integrated at the buried interface of 3D perovskite solar cells (PSCs) to boost device performance and operational stability. The method improves the crystallization quality of perovskite films and reduces defect concentrations at the buried interfaces by more than 90%.
A major 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 (SnO2) nanoparticles, yielding the modified material SnO2-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 used the novel SnO2-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 cm2), 23.44% for a module with an aperture area of 21.54 cm2 (certified at 22.68%), and 22.22% for a large-area module with an aperture area of 64.80 cm2.
This work paves the way for fabricating 2D/3D heterojunctions at the buried interface of perovskite absorber layers and may accelerate the commercial application of perovskite photovoltaic technology.
