One-step thermal engineering of FTO substrate: unlocking higher-efficiency perovskite solar cells

Interfacial energy level alignment is crucial for minimizing efficiency loss in perovskite solar cells (PSCs), yet the energy level matching between transparent conductive oxide (TCO) electrode and electron or hole transport layer (ETL/HTL) has received limited attention. Here, rather than directly employing commercial fluorine-doped tin oxide (C-FTO) as the TCO electrode, a facile one-step thermal treatment strategy was applied prior to the fabrication of n-i-p PSCs. Notably, under thermal treatment at optimal 300 °C, the work function of C-FTO effectively reduced, enhancing the energy level alignment with the ETL. Moreover, the 300 °C-treated FTO (300-FTO) exhibits a smoother surface morphology, improved conductivity and reduced resistivity. These improvements contribute to superior interfacial compatibility with the ETL, facilitating the deposition of high-quality perovskite active layers and promoting more efficient charge transfer and collection. As a result, PSCs based on 300-FTO achieved an average power conversion efficiency (PCE) of 23.02 %, making a significant improvement of 2.7 % compared to devices utilizing untreated C-FTO. This work demonstrates the great efficacy of thermal treatment in modifying FTO, providing a simple and efficient approach for the development of higher-efficiency PSCs.