Bonding of GaAs PV cells on copper substrate by thermocompression for photovoltaic-thermoelectric hybridization

Photovoltaic-thermoelectric hybridization is a pathway to produce electric power using the heat generated in a photovoltaic cell as a heat source for a Seebeck thermoelectric generator. However, previous studies showed the need to reduce the thermal resistance between the photovoltaic cell and the thermoelectric generator to achieve high power conversion efficiency. To reduce this thermal resistance, we propose in this study a method for transferring the cell onto a custom copper substrate and removing the growth substrate from the epitaxial layer by Au-Au interdiffusion bonding and full-substrate etching. Using various methods of characterization, we identify the challenges in each process step for upscaling this process on a larger surface. The first cell transfer attempt achieved a mirror-like surface roughness on the epitaxial layer. Analysis of the defects caused by the bonding and the etching step allows us to identify optimizations to apply the process to centimeter-scale areas.