Delta-Doping Effects on Quantum-Dot Solar Cells

The effects of delta-doping InAs quantum-dot (QD)-enhanced GaAs solar cells were studied both through modeling and device experimentation. Delta doping of two, four, and eight electrons per QD, as well as nine holes per QD, was used in this study. It was observed that QD doping reduced Shockley-Read-Hall recombination in the QDs, which results in a reduced dark current and an improved open-circuit voltage over undoped QD devices. A voltage recovery of 121 mV was observed for the eight-electron sample compared with the undoped sample. QD doping had no positive effects on subbandgap photon collection but actually degraded bulk and QD response as doping levels were increased by limiting minority carrier collection through the QD region. Despite this, an absolute AM0 efficiency improvement of 1.41% was observed for the four-electron sample over the undoped QD device while maintaining a current enhancement.