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Simulation study of GaAsP/Si tandem cells including the impact of threading dislocations on the luminescent coupling between the cells

Onno, AL; Harder, NP; Oberbeck, L; Liu, H; (2016) Simulation study of GaAsP/Si tandem cells including the impact of threading dislocations on the luminescent coupling between the cells. In: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V. (pp. 97431B). SPIE Green open access

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Abstract

A model, derived from the detailed balance model from Shockley and Queisser, has been adapted to monolithically grown GaAsP/Si tandem dual junction solar cells. In this architecture, due to the difference of lattice parameters between the silicon bottom cell – acting as the substrate – and the GaAsP top cell, threading dislocations (TDs) arise at the III-V/Si interface and propagate in the top cell. These TDs act as non-radiative recombination centers, degrading the performances of the tandem cell. Our model takes into account the impact of TDs by integrating the NTT model developed by Yamaguchi et. al.. Two surface geometries have been investigated: flat and ideally textured. Finally the model considers the luminescent coupling (LC) between the cells due to reemitted photons from the top cell cascading to the bottom cell. Without dislocations, LC allows a greater flexibility in the cell design by rebalancing the currents between the two cells when the top cell presents a higher short-circuit current. However we show that, as the TD density (TDD) increases, non-radiative recombinations take over radiative recombinations in the top cell and the LC is quenched. As a result, non-optimized tandem cells with higher short-circuit current in the top cell experience a very fast degradation of efficiency for TDDs over 10^4cm^-2. On the other hand optimized cells with matching currents only experience a small efficiency drop for TDDs up to 10^5cm^-2. High TDD cells therefore need to be current-matched for optimal performances as the flexibility due to LC is lost.

Type: Proceedings paper
Title: Simulation study of GaAsP/Si tandem cells including the impact of threading dislocations on the luminescent coupling between the cells
Event: SPIE OPTO - 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: 10.1117/12.2211113
Publisher version: http://dx.doi.org/10.1117/12.2211113
Language: English
Additional information: Copyright XXXX (year) Society of Photo Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this publication for a fee or for commercial purposes, or modification of the contents of the publication are prohibited. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Dual-junction, Silicon, GaAsP, Threading dislocation density, Luminescent coupling, Model
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/1476754
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