Abstract

One of the requirements for strong subbandgap photon absorption in the quantum-dot intermediate-band solar cell (QD-IBSC) is the partial filling of the intermediate band. Studies have shown that the partial filling of the intermediate band can be achieved by introducing Si doping to the QDs. However, the existence of too many Si dopants leads to the formation of point defects and, hence, a reduction of photocurrent. In this study, the effect of Si doping on InAs/GaAs QD solar cells with AlAs cap layers is studied. The AlAs cap layers prevent the formation of the wetting layer during QD growth and reduce the Si doping density needed to achieve QD state filling. Furthermore, the passivation of defect states in the QD with moderate Si doping is demonstrated, which leads to an enhancement of the carrier lifetime in the QDs and, hence, the open-circuit voltage.

Highlights

  • S INCE the concept of the intermediate-band solar cell (IBSC) was proposed in 1997, significant efforts have been made to realize Intermediate-band solar cells (IBSCs) with efficiencies that exceed the Shockley–Queisser limit of 31% [1]

  • One of the candidates for the high-efficiency IBSC is the quantumdot intermediate-band solar cell (QD-IBSC), which utilizes the discrete nature of the carrier density of states and the bandgap tunability of quantum dots (QDs)

  • An improvement in the VOC (∼44 mV) has been achieved by introducing direct Si doping to QDs with AlAs cap layer (CL)

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Summary

INTRODUCTION

S INCE the concept of the intermediate-band solar cell (IBSC) was proposed in 1997, significant efforts have been made to realize IBSCs with efficiencies that exceed the Shockley–Queisser limit of 31% [1]. Luque and Martı proposed the use of doping as a method to achieve partial filling of the confined states in the IB [17] It has been demonstrated, by Martı et al [18], that half-filling of the IB can be realized by doping the capping layers of QDs with Si in InAs/(Al, Ga)As quantum dot solar cells (QDSCs). The saturation of strain-induced dislocations and QD state filling are demonstrated by direct Si doping of InAs/GaAs QDSCs with AlAs CLs. Previously, we reported that the deposition of AlAs CLs on InAs QDs could suppress the formation of the WL [8].

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