Solar Energy, Vol.195, 6-13, 2020
Transfer printing of fully formed microscale InGaP/GaAs/InGaNAsSb cell on Ge cell in mechanically-stacked quadruple junction architecture
To bypass the requirements of epitaxial and current matching in monolithic stacks, we have finished the transfer printing of fully formed, thin-film microscale triple-junction (3J) solar cells with band gaps of 1.9/1.4/1 eV onto Ge cell to obtain a four-terminal quadruple-junction architecture. Meanwhile, AFM results suggest that both 3J cell and Ge cell have smooth surfaces, in favor of transfer printing with thin adhesive. In addition, the electrical, optical and thermal measurements have confirmed that the TiO2/SiO2/TiO2 film serves as an electrically-insulating, optically-transparent and thermally-conductive interface material. Moreover, colorized infrared optical images of an assembled 3J/Ge cell before and after thermal cycling confirm the interface bonding with high uniformity and indicate no degradation and high thermal stability of interface bonding. Due to the logarithmic increase of V-oc with illumination intensity, the efficiency of both 3J cell and Ge cell from 1 sun and 330 suns have kept increasing from 31.3% to 41.4% and from 0.71% to 1.45%, respectively.