Optimization and performance analysis of thin-film thickness in suspended-structure InGaN/GaN MQW solar cells

This study presents the fabrication and performance evaluation of suspended InGaN/GaN multiple quantum well (MQW) solar cells on silicon substrates, with a focus on the influence of epitaxial layer thickness. By applying inductively coupled plasma (ICP) etching on the epitaxial layer from the backside of the silicon substrate for 0, 5, and 10 minutes, three solar cell samples with different epitaxial thicknesses were prepared, followed by comprehensive morphological characterization and evaluation of electrical and optical properties. The results indicate that reducing the epitaxial layer thickness significantly improves device performance. Specifically, the 5-minute etched sample exhibited the highest short-circuit current, open-circuit voltage, fill factor, and power conversion efficiency, benefiting from reduced series resistance, enhanced carrier collection, and improved EQE. However, excessive thinning due to 10-minute etching introduced interfacial defects which increased carrier recombination, and degraded performance. These findings highlight that moderate thinning of the epitaxial layer is key to balancing optical absorption and carrier transport, thereby optimizing the performance of InGaN/GaN MQW solar cells. This work offers valuable insights into structural design strategies for high-efficiency III-nitride photovoltaic devices.