Defect mediated extraction in InAs/GaAs quantum dot solar cells

Embedding quantum dots into the intrinsic layer of a p-i-n solar cell has been proposed as a method of increasing solar cell photocurrent by improving its long-wavelength light response. However, strong carrier localization and efficient radiative recombination in quantum dots are large barriers to efficient carrier extraction. We present experimental evidence and a theoretical model to show that carrier extraction from InAs quantum dots is significantly enhanced by the presence of defects, which act to lower the potential barrier for carrier escape. Therefore in the long-wavelength region where the quantum dots are strongly absorbing we suggest that contrary to bulk systems, radiative, rather than non-radiative, processes appear to limit the performance of quantum dot solar cells. (C) 2012 Elsevier B.V. All rights reserved.