Growth and Characterization of InAs Quantum Dot Enhanced Photovoltaic Devices

Abstract

The growth of InAs quantum dots (QDs) by organometallic vapor phase epitaxy (OMVPE) for use in GaAs based photovoltaics devices was investigated. Growth of InAs quantum dots was optimized according to their morphology and photoluminescence using growth temperature and V/III ratio. The optimized InAs QDs had sizes near 7×40 nm with a dot density of 5(±0.5)×1010 cm-2. These optimized QDs were incorporated into GaAs based p-i-n solar cell structures. Cells with single and multiple (5x) layers of QDs were embedded in the i-region of the GaAs p-i-n cell structure. An array of 1 cm2 solar cells was fabricated on these wafers, IV curves collected under 1 sun AM0 conditions, and the spectral response measured from 300-1100 nm. The quantum efficiency for each QD cell clearly shows sub-bandgap conversion, indicating a contribution due to the QDs. Unfortunately, the overarching result of the addition of quantum dots to the baseline p-i-n GaAs cells was a decrease in efficiency. However, the addition of thin GaP strain compensating layers between the QD layers, was found to reduce this efficiency degradation and significantly enhance the subgap conversion in comparison to the un-compensated quantum dot cells.

Epitaxial nanowire formation in metamorphic GaAs/GaPAs short-period superlattices

“…During growth of GaAs/GaPAs SPSs, the temperature was alternated periodically between 575 • C for GaPAs (barrier) layers (36 s/layer) and 475 • C for GaAs (well) layers (40 s/layer). Following the method of Hubbard et al, 28 the lower well-layer temperature was used to enhance nanostructure formation. The targeted growth rate was switched between 5.8 nm/min for the barrier layers and 1.7 nm/min for the well layers.…”

Quantum mechanical effects analysis of nanostructured solar cell models

“…Based on the spontaneous emission model, Figures 8 and 9 display the electroluminescence of the p-i-n device due to varying thicknesses of the InAs wells. The literature indicates an electroluminescence of ∼1050 nm for 6 nm quantum dots [11]. In this paper, we have presented a few modeling solutions necessary for the analysis of the next generation of PV devices.…”

Trends, Challenges and Opportunities in Advanced Solar Cells Technologies and PV Market

“…(ii) Following the placement of InAs quantum wells in the i-layer of a GaAs p-i-n cell, there are analysed the quantum confined regions and determined the properties of the eigenstates located therein. (iii) The electroluminescence that occurs due to the nanostructured regions is simulated and discussed [16]. [23].…”