Long Carrier Lifetime in Ultrahigh-Density InAs Quantum-Dots Sheet of Intermediate Band Solar Cells

Miyuki Shiokawa, Edes Saputra, Katusyoshi Sakamoto, Koichi Yamaguchi University of Electro-Communications, Chofu, Tokyo, Japan

Intermediate band solar cells (IB-SC) using self-assembled semiconductor quantum dots (QDs) with ultrahigh density have attracted considerable interests for achievement of high conversion efficiency. In this study, in-plane ultrahigh-density InAs QDs with 3 – 5 × 10¹¹ cm⁻2 were grown on GaAsSb/GaAs(001) by molecular beam epitaxy. The ultrahigh density QDs with small size revealed abnormal photoluminescence (PL) properties, including excitation power dependences of PL peak energy and temperature dependences of PL peak energy and PL full width at half maximum (FWHM). These results suggested in-plane electronic coupling in the ultrahigh density QD sheet with small size, which provided localized minibands. For laterally coupled QD sheet, long PL decay time of 4 – 6 ns was observed, spite of type-1 band alignment. The PL decay time drastically decreased by reverse electric field. It could be explained by electronic state transition from 2-dimensional to zero-dimensional. The ultrahigh-density InAs QD sheets are promising structures for development of the IB-SCs with high performance.