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1.7eV Al0.2Ga0.8As solar cells epitaxially grown on silicon by SSMBE using a superlattice and dislocation filters

Onno, AL; Wu, J; Jiang, Q; Chen, S; Tang, M; Maidaniuk, Y; Benamara, M; ... Liu, H; + view all (2016) 1.7eV Al0.2Ga0.8As solar cells epitaxially grown on silicon by SSMBE using a superlattice and dislocation filters. In: Freundlich, A and Lombez, L and Sugiyama, M, (eds.) Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V. Society of Photo-Optical Instrumentation Engineers (SPIE): San Francisco, CA, USA. Green open access

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Abstract

Lattice-mismatched 1.7eV Al0.2Ga0.8As photovoltaic solar cells have been monolithically grown on Si substrates using Solid Source Molecular Beam Epitaxy (SSMBE). As a consequence of the 4%-lattice-mismatch, threading dislocations (TDs) nucleate at the interface between the Si substrate and III-V epilayers and propagate to the active regions of the cell. There they act as recombination centers and degrade the performances of the cell. In our case, direct AlAs/GaAs superlattice growth coupled with InAlAs/AlAs strained layer superlattice (SLS) dislocation filter layers (DFLSs) have been used to reduce the TD density from 1×10^9cm^-2 to 1(±0.2)×10^7cm^-2. Lattice-matched Al0.2Ga0.8As cells have also been grown on GaAs as a reference. The best cell grown on silicon exhibits a Voc of 964mV, compared with a Voc of 1128mV on GaAs. Fill factors of respectively 77.6% and 80.2% have been calculated. Due to the lack of an anti-reflection coating and the non-optimized architecture of the devices, relatively low Jsc have been measured: 7.30mA.cm^-2 on Si and 6.74mA.cm^-2 on GaAs. The difference in short-circuit currents is believed to be caused by a difference of thickness between the samples due to discrepancies in the calibration of the MBE prior to each growth. The bandgap-voltage offset of the cells, defined as Eg/q-Voc, is relatively high on both substrates with 736mV measured on Si versus 572mV on GaAs. The non-negligible TD density partly explains this result on Si. On GaAs, non-ideal growth conditions are possibly responsible for these suboptimal performances.

Type: Proceedings paper
Title: 1.7eV Al0.2Ga0.8As solar cells epitaxially grown on silicon by SSMBE using a superlattice and dislocation filters
Event: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V
Location: San Francisco, USA
Dates: 15 February 2016 - 17 February 2016
Open access status: An open access version is available from UCL Discovery
DOI: 10.1117/12.2208950
Publisher version: http://dx.doi.org/10.1117/12.2208950
Language: English
Additional information: Copyright © 2016 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Keywords: III-V on silicon, AlGaAs solar cell, MBE, Threading dislocation density, Dislocation filter, Superlattice
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/1476750
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