Bonding III–V/Textured‐Silicon Monolithic Flexible Tandem Devices

Abstract III–V/silicon tandem solar cells simultaneously have the potential advantages of high efficiency and low cost. Bonding is an effective way to realize tandem at both ends. However, it is difficult to realize vacuum bonding in industrialized micrometer‐sized pyramid silicon cells. Up to know, all bonding in III–V/silicon tandem solar cells is based on planar silicon cells. Here, a transparent conductive adhesive (TCA) based on micron particle size is designed and implemented, which realizes the bonding of III–V cell and textured silicon cell for the first time. The TCA consists of epoxy adhesive 301 (Epoxy‐301) as transparent adhesive and silver‐coated flexible polymethylmethacrylate microspheres as conductive particles. The average contact resistance of TCA is 0.17 Ω cm 2 , and the transmittance exceeds 91% in the range of 800—1200 nm. In addition, TCA shows good stability in the etching process of GaAs substrates. Monolithic III–V/silicon device exhibits 25.1% power conversion efficiency (PCE) on thin and textured silicon heterojunction solar cells, which enables flexible properties of tandem cells. Compared with silicon subcell and III–V subcell, the performance of tandem device is improved by 28.3% and 8.6%, respectively. This strategy provides a broad research window for improving the performance of tandem solar cells based on industrialized textured‐silicon bottom cells.