Development of hermetic glass frit encapsulation for perovskite solar cells

A hermetic laser-assisted glass frit encapsulation, at a process temperature of 120 °C, was developed for perovskite solar cell application. The hermeticity and long-term stability of the sealing was examined based on standard tests for photovoltaic (PV) applications. Encapsulations using fluorine doped tin oxide (FTO)-coated glass substrates displayed 8.93 × 10−8 atm cm3 s−1 air leak rate after five cycles of a humidity-freeze test according to the IEC61646 standard; a rate lower than the reject limit of the MIL-STD-883 standard test for fine leaks. Devices sealed with a TiO2 blocking layer and FTO scribing—denoted as an empty perovskite solar cell—showed that the encapsulation is compatible with the various thermal coefficient of expansion regions of perovskite solar cells (PSCs). The applicability of the MIL-STD-883 standard was studied in detail and it was concluded that a new method is required to measure the fine helium leak rate of devices with cavity sizes larger than 5.5 × 5.5 cm2. The developed sealing process is scalable for larger devices; therefore, it guarantees a new step forward for the industrialization of PSCs.