Direct femtosecond laser welding of silica glass for perovskite film encapsulation

The environmental sensitivity of perovskite solar cells (PSCs) significantly hinders their commercial viability. A currently employed method for encapsulating perovskite solar cells is the use of potting compounds. However, adhesive-based encapsulation suffers from inherent drawbacks, such as susceptibility to aging and volatilization, which ultimately compromise the long-term reliability, stability, and lifetime of the solar cells. This study developed a novel method using a femtosecond laser (1030 nm wavelength, 300 fs pulse width) to directly weld silica glass for perovskite film encapsulation. By optimizing processing parameters (single-pulse energy: 1.37μJ, repetition rate:1 MHz), localized melting and recrystallization were induced at the indium tin oxide (ITO)/silica glass interface, achieving covalent bonding. The optimized weld lines exhibited a high shear strength of 147.6 MPa and formed a continuous molten transition zone at the interface. This high strength indicates excellent mechanical stability of the laser-welded encapsulation. After enduring 10 thermal cycles (between 85°C and −20°C) and 168 h of water immersion, the encapsulated samples maintained structural integrity without color degradation or decomposition. These results highlight the reliability of this encapsulation method under extreme environmental conditions. To our knowledge, this work represents the first demonstration of long-term hermetic sealing of perovskite films using femtosecond lasers, overcoming the limitations of traditional adhesive encapsulation (prone to aging and volatilization) and the insufficient stability (less than 6 h) of picosecond laser sealing. This work not only provides a highly reliable encapsulation solution for environmentally sensitive optoelectronic devices, but also paves the way for the monolithic integration and commercialization of perovskite-based optoelectronics.