Effect of Position-Dependent Doping on Intermediate Band Generation-Recombination Rate in InAs/GaAs Quantum Dot Solar Cell

Abstract

InAs/GaAs quantum dot solar cells (QDSCs) with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -type delta-doped quantum dots (QDs) have gained immense interest due to their improved open-circuit voltage. Here we report the effect of position-dependent doping on the intermediate band generation-recombination rate through theoretical modelling to analyze the reduced short-circuit current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_SC</i> ) due to doping. A 1-D drift-diffusion model was used to obtain the photovoltaic characteristics. Simulations suggest that the intermediate band's contribution reduces by almost three orders of magnitude for the doped case near the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -doped base at short-circuit conditions compared to the undoped case. We utilized these findings to develop spatially varying doping conditions. The structure with doped QDs exhibit the highest power conversion efficiency (PCE) but minor <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_SC</i> enhancement. Comparatively, when the QDs near the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -doped base are kept undoped, better results are obtained at low bias, and a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_SC</i> enhancement of 0.322 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is observed. With the increase in bias above 0.68V, recombination becomes dominant in the proposed partially doped structure. These observations are backed by the occupation probability of the QDs, electron and hole carrier dynamics, and electric field distribution along the intrinsic region. With such an arrangement, PCE is enhanced by 0.69% compared to that of the undoped QDSC.