Title :
GaAs and Al0.2Ga0.8As solar cells with an indirect-bandgap Al0.8Ga0.2As emitter-heterojunction cells
Author :
Venkatasubramanian, R. ; Timmons, M.L. ; Hutchby, J.A. ; Field, H. ; Emery, K.
Author_Institution :
Res. Triangle Inst., Research Triangle Park, NC, USA
Abstract :
We first present a high-performance p+ Al0.8Ga0.2As-n GaAs heterojunction (HJ) cell, where the conventional p+GaAs emitter has been replaced by a p+ Al0.8Ga0.2As hetero-emitter. The total thickness of the p+ Al0.8Ga0.2As hetero-emitter is about 0.1 μm, about twice that of window-layer thickness in conventional GaAs homojunction cells. The NREL-measured AM1.5G data on such a GaAs HJ cell include a VOC of 1.029 Volts, a JSC of 25.4 mA/cm2, a fill-factor of 0.8279, and a total-area η of 21.6%. The relatively high VOC of the cell indicates no deleterious effect in placing the Al0.8Ga0.2As-GaAs hetero-interface in the depletion layer. For a given set of n-GaAs base and back-surface field layer, this HJ cell has exhibited superior blue performance compared to a conventional GaAs homojunction cell (p+GaAs emitter of 0.2-μm-thickness and doped to about 2×1018 cm-3 ). Second, we describe a high-performance n+ Al0.8 Ga0.2As-Al0.8Ga0.2As HJ cell, where the conventional n+ Al0.8Ga0.2As emitter has been replaced by a n+ Al0.8Ga0.2 As hetero-emitter. This HJ cell has helped us to obtain a significant and reproducible improvement in the cell performance (AM1.5, η=18.1%) over conventional Al0.8Ga0.2As homojunction cells (AM1.5, η=11.1%). This Al0.8Ga0.2 As HJ cell indicates a 42% improvement in JSCa VOC increase of almost 110 mV, and an improved fill-factor, compared to homojunction cells. The improved JSC is a result of higher blue-response and an enhanced red-response
Keywords :
III-V semiconductors; aluminium compounds; energy gap; gallium arsenide; p-n heterojunctions; semiconductor materials; solar cells; 1.029 V; 21.6 percent; Al0.2Ga0.8As-Al0.2Ga0.8 As; Al0.2Ga0.8As-Al0.2Ga0.8 As solar cell; Al0.2Ga0.8As-GaAs; Al0.2Ga0.8As-GaAs solar cell; Al0.8Ga0.2As-Al0.8Ga0.2 As; NREL-measured AM1.5G data; blue performance; depletion layer; enhanced red-response; fill-factor; high-performance; indirect-bandgap Al0.8Ga0.2As emitter-heterojunction cells; p+ Al0.8Ga0.2As hetero-emitter; performance improvement; saturation dark current density; total-area efficiency; Ambient intelligence; Dark current; Gallium arsenide; Heterojunctions; Laboratories; Light emitting diodes; Molecular beam epitaxial growth; Photovoltaic cells; Renewable energy resources; Reproducibility of results;
Conference_Titel :
Photovoltaic Energy Conversion, 1994., Conference Record of the Twenty Fourth. IEEE Photovoltaic Specialists Conference - 1994, 1994 IEEE First World Conference on
Conference_Location :
Waikoloa, HI
Print_ISBN :
0-7803-1460-3
DOI :
10.1109/WCPEC.1994.520723
