Effect of cell size on GaAs concentrators with InAs quantum dots

GaAs solar cells with varying layers of QDs and varying cell size (to vary perimeter to area ratio) were fabricated. Cells were tested using an I_SC-V_OC method to determine local ideality factors, as well as to extract recombination currents at low and high bias. Baseline devices without QDs were also simulated using SILVACO to analyze the effects of simply increasing the i-region thickness, a consequence of adding QD layers. Results show ideality factors of QD cells have a more prominent dependence on cell size than the baseline at low bias, but exhibit reduced ideality compared to baseline at and beyond 1-sun bias conditions. The former may be attributed to the dominant influence of sidewall states in QD structures in the space charge region at low injection, while the latter may be due to a dominant recombination mechanism through radiative QD states at higher injection. The dark current associated with operational bias at 1-sun and above exhibited a reduced dependence on cell size for QD devices compared to the baseline.