Impact of electron and heavy hole confinement depth ratio on the performance of III–V p-i-n multi-quantum well solar cells

A number of III–V p-i-n multi-quantum well solar cells exhibiting identical p and n regions, similar intrinsic region thickness and radiative recombination energies but varying well composition and thickness are investigated. Theoretically calculated electron and hole confinement depths varied among samples due to differences in well material parameters. The ratio of electron confinement depth to the total offset in optical band-gap was found to vary between samples. Those exhibiting smaller ratios were systematically found to perform better. In addition, the effective potential barrier encountered by one of the carriers was found to match the radiative recombination activation energy determined from photoluminescence measurements. Devices with better photovoltaic characteristics were found to display radiative recombination activation energies directly proportional to their respective electron confinement depth. These observations are tentatively explained in terms of carrier dynamics occurring in the intrinsic region