Dependence of device performance on carrier escape sequence in multi-quantum-well p-i-n solar cells

Abstract

This work is a study relating device performance and carrier escape sequence in a large set of InAsP∕InP p-i-n multi-quantum-well solar cells. The devices encompass nearly identical i-region thickness and built-in electric field and present similar absorption threshold energies. The escape sequence of the first confined electron-to-conduction band continuum and heavy/light holes-to-valence band continuum is extracted from the photoluminescence versus temperature analysis and by comparing the measured activation energies to calculated hole/electron well depths and thermionic escape times. Light holes, as expected for most III-V nanostructure systems, are found to be the fastest escaping carriers in all samples. The escape of electrons prior to heavy holes is shown to be a prerequisite to prevent severe open circuit voltage degradation. A possible explanation of the origin of this effect is offered. InP∕InAsP multi-quantum-well solar cells with high built-in electric field and fast electronic escape time display better open circuit voltage and performance.