Nanoscale optimization of quantum dot media for effective photovoltaic conversion

摘要

Nanoscale engineering of band profile and potential profile provide effective tools for the management of photoelectron processes in quantum dot (QD) photovoltaic devices. We investigate the QD devices with various 1-μm InAs /GaAs QD media placed in a 3-μm base GaAs p-n junction. We found that n-charging of quantum dots (QDs) create potential barriers around QDs. QD growth between ultrathin AlGaAs layers leads to the formation of AlGaAs "fence" barriers, and reduces the wetting layers (WLs). The barriers around QDs and reduction of the wetting layer substantially suppress recombination processes via QDs. The n-doping of interdot space in QD media enhances electron extraction from QDs. All of our QD devices show short-circuit current, J_(SC), higher than that of the reference cell, but smaller open-circuit voltage, V_(OC).. In the QD devices, the short circuit currents increase by ～0.1 mA/cm~2 per dot layer. J_(SC) reaches 28.4 mA/cm~2 in the device with QD media that combines dot charging, fence barriers, and WL reduction.