Effects of Temperature on I-V Characteristics of InAs/GaAs Quantum-Dot Solar Cells

The current-voltage (I-V) characteristics of quantum-dot (QD) solar cells under illumination at various temperatures are presented. Stacked of high-density self-assembled InAs/GaAs QDs were incorporated into the Schottky-barrier-type solar cell structure. The I-V characteristics reveal that both short-circuit current and open-circuit voltage of the QD solar cell reduce when the measurement temperature increases. This result is unexpected and inconsistent with a basic solar cell theory where the temperature is believed to cause the enhancement of the short-circuit current. By considering the solar-cell circuit model, we can explain the obtained I-V curves by a high series resistance of the cell structure. Theoretical exclusion of the series resistance shows a substantial improvement of solar cell fill factor and efficiency. This work therefore suggests that reduction of series resistance by properly doping of the epitaxial layers can improve these devices.