InAs quantum dot enhancement of GaAs solar cells

Abstract

A series of InAs QD enhanced solar cells has been grown with arrays of 10, 20, 40, 60 and 100 layers of QDs in the GaAs i-region. An enhancement in short circuit current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ) using QDs was observed. QD cells with up to 40 layers show a 1.4 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> improvement in J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> compared to a GaAs control cell grown without QDs. In addition, the a high open circuit voltage of 0.88 V was maintained till 60 layers of QD. While the 100 layer QD cell shows degradation in the emitter region, the QD contributed current, due to GaAs sub-bandgap absorption, was maintained at 2.7 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This amount of current tuning, if applied to the middle current limiting junction in a triple junction cell, would lead to ~3% absolute increase in efficiency.