AlGaAs/GaAs heterostructure solar cells

Abstract

Eight structures of Heterostructure Solar Cells have been designed and fabricated, by Molecular Beam Epitaxy (MBE) and by Liquid Phase Epitaxy (LPE) technologies. The first group, which consists of six structures: one of GaAlAs Schottky Barrier Diode, one of constant band gap window layer GaAlAs(p)/GaAs(n) heterojunction and three of step or stair case band gap window layer GaAlAs(n)/GaAs(p) heterojunction were realized by MBE, whereas the other two structures of constant band gap window layer GaAlAs(P)/GaAs(n) heterojunction were produced by LPE. Optical and electrical properties of all samples were then examined. It is evident that the GaAlAs wide band gap window layer of all heterostructure solar cells can behave in the role of window effect but it can not improve the overall performance of solar cells as expected. In conclusion, these solar cells perform at 1 sun with short circuit current (I[subscript sc]) in the range of 0.6 to 1.5 , open circuit voltage (V [subscript oc) in the range of 0.43 to 0.7 Volt, maximum output power (P [subscript max) in the range of 0.15 to 0.5 , fill factor (FF) in the range of 0.38 to 0.61 and efficiency (η) in the range of 2.3 to 5 %. The main reasons that cause all samples to have low performance are due to low quality of the crystal layers and of junction interface, together with unsuitable designed structures.