Self-Encapsulated Semitransparent Perovskite Solar Cells for Long-term Stability via Thermocompression Bonding Process

Organic-inorganic hybrid perovskite solar cells (OIHPs) have attracted the PV community due to low cost and high power conversion efficiency, but still have suffered from poor stability. In order to shield perovskite solar cells (PSCs) from extrinsic degradation factors such as oxygen and moisture and assure long-term stability, effective encapsulation technology is indispensable. Here we designed a facile process to build glass-glass encapsulated semitransparent PSCs by laminating two half cells where a perovskite layer is formed on a hole transport layer (HTL, p-type) and an electron transport layer (ETL, n-type), respectively, with a transparent conducting oxide (TCO) glass substrate. By laminating the half cells through a thermocompression bonding process, the device is self-encapsulated during manufacturing. Soft mechanical characteristics and atomic migration nature of the perovskites enable the lamination between the perovskite layers with minimizing voids and good adhesion properties. During the lamination process, surface of the perovskite transformed into bulk with enlarged grains, and the interfaces has much smoother and denser morphology. Through surface iodine extraction experiments and TRPL analysis, it was confirmed that defects and trap density decreased in the laminated perovskite. The thermcompression increases hydrophobicity on interfaces of the perovskite. Therefore, the laminated perovskite has higher stability against moisture. The self-encapsulated semitransparent PSCs with a wide bandgap perovskite (E_g ~ 1.67eV) is performed with the PCE of 17.24 %, and thermal stability at 85 °C is secured for over 3,000 hours.