Ultrathin Multiple Quantum Wells Solar Cell Based on Silicon/Germanium Nanostructures

In this work, we report a proof-of-concept for an ultrathin multiple quantum wells (MQW) solar cell based on silicon (barrier)/germanium (QW) heterostructures integrated as a subwavelength photonic resonator below 50 nm. The multiplication of the QWs number in a periodic configuration of 6 times 2.5 nm-thick QWs allows the enhancement of photocurrent while maintaining high voltage and fill factor. Compared to a single QW (SQW) nanoabsorber of 20 nm, the implementation of MQW architecture with similar total thickness results in a significant enhancement of the photoconversion efficiency from 3 % to 5%, yielding a relative improvement of about 65%. Based on optoelectronic modeling of the optical field distribution and the electronic structure at the QW/barrier heterojunctions, the output characteristics of the subwavelength MQW solar cell device are analyzed.