Optical Design and Bandgap Engineering in Ultrathin Si/Ge Multiple Quantum Wells Solar Cell

Kurzfassung

Emerging photovoltaics (PV) enable multifunctional utilization in versatile applications beyond massive electricity production by conventional PV technologies. Novel functional materials and innovative device architectures are sought of to provide tunable solar cells with customized design capabilities. In this work, we present the optical design and bandgap engineering features in ultrathin hydrogenated amorphous Si/Ge multiple quantum well (MQW) solar cell integrated as a photonic nanocavity. Optically, the absorption resonance condition, the absorption edge and the resulting photocurrent outputs are strongly modulated by changing the period thicknesses, the numbers and the positions of QWs inside the deep-subwavelength nanophotonic resonator. Regarding the electronic aspect, the photovoltage and the carrier collection efficiency are strongly thickness-dependent due to the tuning of QW bandgap and QW/barrier band heterojunction band offset under quantum confinement effect. The established design rules along our study can be extended for the development of relevant multifunctional semitransparent PV devices as well as ultrathin PV based on quantum-confined nanostructures from different material systems.