Effects of AlGaAs energy barriers on InAs/GaAs quantum dot solar cells

Abstract

We have studied the effects of AlGaAs energy barriers surrounding self-assembled InAs quantum dots in a GaAs matrix on the properties of solar cells made with multiple quantum dot layers in the active region of a photodiode. We have compared the fenced dot samples with conventional InAs/ GaAs quantum dot solar cells and with GaAs reference cells. We have found that, contrary to theoretical predictions, the AlGaAs fence layers do not enhance the transport properties of photogenerated carriers but instead suppress the extraction of the carriers excited in the dots by light with wavelengths longer than the cutoff wavelength of the GaAs matrix material. Both the standard quantum dots and the fenced dots were found to give solar cell performance comparable to the GaAs reference cells for certain active region thicknesses but neither showed enhancement due to the longer wavelength absorption or improved carrier transport.

The role of intersubband optical transitions on the electrical properties of InGaAs/GaAs quantum dot solar cells

“…The QDSC has a 5.8% increase of the short‐circuit current density (Jsc) and a 16% decrease of the Voc compared with the reference cell, leading to an overall reduction in efficiency from 14.3% to 12.3%. This result is consistent with other reports , and the increased Jsc of the QDSC further indicates that the QDs are of high optical quality. The room temperature spectral response and photoluminescence spectrum are plotted together in Figure .…”

“…Sablon et al . reported that additional AlGaAs barrier layers surrounding QDs inhibited the extraction of carriers from bound states. The use of thin high bandgap barrier layers surrounding QD layers can have the added property of suppressing sub‐bandgap 2D wetting layer transitions, thus allowing only the generation of 0D QD sub‐bandgap transitions.…”

“…Theoretical studies of intermediate band solar cells have predicted potential efficiencies as high as 70% under full concentration for ideal devices , compared with 40.7% for a conventional single junction device. The use of quantum dots (QDs) for the implementation of intermediate band solar cells has been proposed , and numerous experimental and theoretical studies of quantum dot solar cells (QDSCs) have been reported . The majority of QDSC research has focused on the In(Ga)As/GaAs material syste,m since the highest measured efficiencies of single junction cells are obtained for GaAs devices, and In(Ga)As/GaAs QDs of very high optical quality can be grown by a self‐assembly process .…”

Enhancement of Surface Diffusivity for Waviness Evolution on Heteroepitaxial Thin Films

“…Investigations show that the maximum power conversion efficiency can be theoretically as high as 45% for a QD solar-cell that has 10~20 layers of indium-arsenide (InAs) QDs encapsulated by an aluminum-gallium-arsenide (AlGaAs) high potential barrier fence under AM1.5 spectral radiation. 4) Although experimental studies [5][6][7][8] at the current stage show lower efficiencies, mostly ranging from 7 to 12%, another theoretical study predicts that it can be as high as 25~50% depending on the precise control of QD dimension and gallium content in In x Ga 1-x N/GaN QD IB solar-cells.…”

An Investigation of the Role of Radiative and Nonradiative Recombination Processes in InAs/GaAs $_{1-x}$ Sb $_{x}$ Quantum Dot Solar Cells

“…Semiconductor quantum dots (QDs) are considered as a candidate system to form such IBs because of the discrete energy levels introduced by the 3-dimensional confinement of QDs. Several QD systems have been investigated over the past decade [4]- [9] where the most well-studied material system for IBSC applications is the InAs/GaAs QD system [4]- [6][9] [11]. Despite significant progress, the practical potential of the InAs/GaAs QD system isl imited by non-optimized spectral overlap and lower QD absorption [13].…”