Control of Hot Carrier Thermalization Rates in Nanowires for Advanced-Concept Photovoltaic Solar Cells

Hot carrier solar cells are a type of 3rd generation photovoltaic devices. The goal of these cells is to increase the efficiency of solar technology beyond the theoretical limit in single-junction devices. To design an efficient hot carrier solar cell, it is necessary to reduce the rates of hot carrier thermalization in solar cell absorbers. Nanowires (NWs) are potential candidates for hot carrier solar cells due to their one-dimensional geometry and density-of-states. In this study, we are examining the hot carrier effects in core-shell InGaAs/InAlAs nanowires (NWs) with diameters ranging from 110 nm to 200 nm. The results of photoluminescence spectroscopy indicate significant correlations between hot carriers and diameter: as the diameter decreases from 200 nm to 160 nm, the hot carrier effects intensify, but further reduction in diameter (< 160 nm) leads to weaker hot carrier effects. The increase of hot carrier effects by reducing the NW diameter (160 nm < d < 200 nm) is caused by the combined effects of phonon bottleneck and Auger heating. Conversely, in the thin NWs, an increase in microstructure disorder results in higher rates of hot carrier thermalization, leading to weaker hot carrier effects. These findings are consistent with both theoretical and experimental studies, including those using time-resolved photoluminescence spectroscopy and high-resolution transmission electron microscopy.