Printing techniques are an attractive industrial pathway towards perovskite solar cells (PSCs) manufacturing due to their compatibility with large-scale, continuous production. However, SnO2 nanoparticles - commonly used as the electron transport layer - tend to aggregate during the printing process, leading to non-uniform film formation. This aggregation introduces crystallization defects in the perovskite layer and creates interfacial charge transport barriers, posing a challenge to further efficiency improvements.
Image credit: Joule
Researchers from China's Dalian Institute of Chemical Physics, Liaoning Normal University, Hubei University, Wuhan Textile University, Zhejiang University, Eastern Institute of Technology, University of Chinese Academy of Sciences and Australia's University of Technology Sydney have developed a layer of “molecular glue” that can effectively anchor the solute that suspends the monodisperse SnO2 nanoparticles into a uniform thin film and adhere it to the top perovskite during the mechanical blading process.
In their new work, the scientists introduced tetramethylammonium chloride (TMACL) into the SnO2 precursor colloidal solution. TMACL, leveraging electrostatic interactions, effectively "anchored" the SnO2 nanoparticles, suppressing their agglomeration and enhancing overall colloidal stability. The surface roughness of the coated film was reduced by 32%, and pinhole defects were minimized.
Moreover, the nitrogen atoms in TMACL formed chemical bonds with lead ions in the perovskite layer, acting as a "molecular glue" that tightly bound the electron transport layer to the perovskite absorber. This strong interfacial connection reduced interface defect density by 40% and substantially improved charge extraction efficiency.
Through this "molecular glue" strategy, the researchers bridged the performance gap between laboratory-scale and large-area devices. They fabricated a perovskite module with an aperture area of 57.20 cm2 entirely through a coating-based process, achieving a power conversion efficiency of 22.76%, with a certified efficiency of 21.60%. The unencapsulated device retained 93.25% of its initial efficiency after 1,500 hours of operation under ambient conditions, which was superior to devices produced by conventional methods.
Furthermore, the strategy proved effective in flexible perovskite solar cells. A flexible module in the same area achieved an efficiency exceeding 20% and maintained 95.3% of its initial performance after 500 bending cycles, highlighting its potential for applications in wearable electronics, vehicle-integrated photovoltaics, and other emerging scenarios.
The strategy can seamlessly integrate with scalable coating and printing processes. Unlike traditional spin-coating, printing allows continuous fabrication of meter-scale films with material utilization rates exceeding 90% and energy consumption being reduced by 50%. In addition, TMACL costs only one-tenth of conventional interface modification materials as it is a widely available industrial reagent, and it eliminates the need for extra processing steps.
"Our study lowers the barriers to large-scale manufacturing and paves the way for the commercial deployment of high-performance perovskite solar technologies," said Prof. Liu Shengzhong from the Dalian Institute of Chemical Physics (DICP).
