A new approach to derive the below‐bandgap absorption in InAs/GaAs self‐assembled quantum dot (QD) devices using room temperature external quantum efficiency measurement results is presented. The significance of incorporating an extended Urbach tail absorption in analyzing QD devices is demonstrated. This tail is used to evaluate the improvement in the photo‐generated current. The wetting layer and QD absorption contributions are separated from the tail absorption. Several absorption peaks due to QD excited states and potentially different size QDs are observed. An inhomogeneous broadening of 25 meV arising from the variance in the size of QDs is derived. Copyright © 2014 John Wiley & Sons, Ltd. The insertion of self‐assembled quantum dots in the crystal lattice leads to a perturbation of the band edge that can be described by an extended Urbach tail. Sources for below‐bandgap one‐photon absorption include tail absorption, quantum dots, and wetting layer absorption. The Urbach tail absorption accounts for 45% of the total below‐bandgap absorption in the tested sample. Besides enhanced photo‐generated current density, the tail absorption is also responsible for the degradation of the open‐circuit voltage.
Below‐bandgap absorption in InAs/GaAs self‐assembled quantum dot solar cells
Progress in photovoltaics ; 23 , 8
2015
Article (Journal)
English
BKL: | 53.36 Energiedirektumwandler, elektrische Energiespeicher |
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