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Optimization of CdTe solar cell performances using Ga-doped MgxZn1-xO buffer layer

Auteurs : Samah BOUDOUR, Idris BOUCHAMA, Moufdi Hadjab
Année : 2016
Domaine : Electronique
Type : Communication
Conférence: 6th International Symposium on Transparent Conductive Materials
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Mots clés : AMPS-1D, Ga-doped MgxZn1−xO, CdTe, Thin film solar cells

Résumé :

In this work, Ga-doped MgxZn1−xO (GMZO) thin films were developed for application as high resistance transparent (HRT) buffer layer (BL) in high efficiency Cadmium Telluride (CdTe) thin films solar cells. As the excellent electrical properties of Ga-doped MgxZn1−xO varied according to the gallium (Ga) and magnesium (Mg) concentration, the use of GMZO thin films as both a buffer layers and/or a transparent conducting oxides (TCO) becomes ever more flexible. We have performed a computer simulation of (n+)-GMZO/n-GMZO/p-CdTe/MoTe2/Mo proposed structure with AMPS-1D software in one dimension under AM1.5G illumination. The structure uses Molybdenum ditelluride (MoTe2) layer as a pseudo contact between the CdTe absorber layer and the Mo back contact. On the basis of a some experimental data, a high transparency and conductive GMZO thin films can be obtained with Ga content around 0.5 at.%, and the high resistive GMZO films with low Ga content (0.05 at. %). With varying the absorber thickness and the carrier concentration, the effect of Mg concentration (x) on the performance of substrate Ga(0.5 at.%)-doped MgxZn1−xO (TCO layer)/Ga(0.05 at.%)-doped MgxZn1−xO (buffer layer)/p-CdTe (absorber layer)/MoTe2/Metal structure was investigated. As a result, an excellent performance can be achieved with high Mg concentration, the current density of about 26.2 mA/cm2 has been obtained for 2 μm-CdTe solar cell using n-type Ga(0.05 at.%)-doped Mg0.15Zn0.85O buffer layer for 200 nm thick. It is also found that a conversion efficiency of more than 20.21 % could be expected for more than 2 μm absorber thickness and acceptor concentration of 1018 cm-3. From the results, we suggest the use of Ga-doped MgxZn1−xO as a buffer and/or window layers, to build high-efficiency CdTe solar cells with optimum photovoltaic parameters.