Perovskite solar cells (PSCs) offer high efficiency and low fabrication costs, making them strong candidates for next-generation photovoltaic technology. Printing techniques have become the preferred industrial pathway among available fabrication methods 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.

In a study published in Joule, a team led by Prof. YANG Dong and Prof. LIU Shengzhong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has addressed this challenge through interface interaction optimization.

Researchers 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, 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 of the same area achieved the 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.