Effects of the substrate temperature on the properties of CdTe thin films deposited by pulsed laser deposition

CdTe solar cells are not only CdS/CdTe p-n junction cells, but also a kind of multilayer thin films solar cells on Transparent-Conducting-Oxide (TCO) substrates. Many techniques can be employed to deposit CdTe films, such as close-spaced deposition (CSS), metal organic chemical vapor deposition (MOCVD) and pulsed laser deposition (PLD). Among them, PLO is a promising and widely-used technique for multilayer thin films deposition. In general, the substrate temperature (T-s) is relatively low during PLD-CdTe thin films deposition processing in vacuum, less than 300 degrees C, which is not that high enough to fabricate high efficiency cells. It is firstly found by us that CdTe film can be deposited on higher temperature Fluorine-Tin-Oxide (FTO) substrates (>= 400 degrees C) under a particular atmosphere by PLO. In this paper, the deposition of CdTe thin films at varying Ts in vacuum condition has been studied thoroughly and strong T-s dependence of the films properties has been revealed. Thus, based on this thorough study, by using the relatively high pressure and high T-s PLD technique, we fabricated an ultra-thin FTO/PLD-CdS(100 nm)/PLD-CdTe(similar to 1.5 mu m)/HgTe:Cu/Ag solar cell with an efficiency of 6.68% in the atmosphere of Ar +O-2 (15 Torr) and at the relatively high T-s (500 degrees C). (C) 2012 Elsevier B.V. All rights reserved.