Fully glass frit encapsulated dye-sensitized solar cells: Challenges for hermetical sealing of electrolyte injection holes

Abstract

Dye-sensitized solar cells (DSSC) are the fastest-evolving indoor PV technology for long-term wireless power for the internet of things (IoT) devices and wireless sensors. Hermetic encapsulation is crucial for the reliable decoupling of extrinsic and intrinsic degradation factors of DSSCs as well as to protect long-lasting devices against moisture, oxygen ingress, and electrolyte leakage. Encapsulating the edges with glass frits has proven the most durable method of overcoming the device's hermeticity challenge. However, sealing the electrolyte injection holes with glass remained an elusive objective achieved in this study by structuring the glass into a capillary shape and laser-induced fusing the capillary edge. The structured injection hole effectively dissipates heat and thermal stress; when the glass sealing temperature reaches around 1200 degrees C, the device's cavity does not exceed 50 degrees C. The method produces sealed devices that passed the MIL-STD-883 helium leakage and the IEC 61646 humidity-freeze tests. After 4336 h of accelerated aging according to ISOS-L-2/3 protocols, entirely glass-sealed DSSCs maintained their photocurrent conversion efficiency (PCE) while conventionally polymer-sealed and partially glass-sealed counterparts exhibit inverse PCE progression, with an average deterioration rate 1.8.10(-3) and 2.2.10(-3) per day, respectively. Full glass encapsulation allows long-life DSSCs and durable long-term stability certification. Extrinsic degradation is prevented and opens a trustworthy assessment of possible intrinsic degradation factors.