Optimisation of CISCuT cell design

The special features of the CISCuT material require cell concepts that diff er from conventional CuInS2 solar cells. For the n-type CISCuT bulk materia l, a p-type buffer is required. In this paper, the currently used p-type Cu (O,S) buffer layer is replaced by the higher bandgap material CuI. On 10-mm (2) cells the efficiency profit made by the replacement of Cu(O,S) with CuI is demonstrated. For larger cell areas, two different cell configurations are described. In the first concept, a ZnO:Al window layer is deposited on top of the CuI buffer layer. The second concept uses a metal grid as a fron t contact. Theoretical considerations point out the consequences of the giv en concepts for the CISCuT cell performance. For the Cu/CISCuT/CuI/ZnO:Al l ayer configuration, an additional tunnel junction is expected at the interf ace between the p-type CuI and the n-type ZnO:Al. In the metal grid concept , CuI doping with iodine is required to lower the sheet resistance of the l ayer. Some precautions against iodine out-diffusion have to be taken. For t he window layer configuration on an area of 400 mm(2), a cell performance o f 5.2% was obtained. (C) 2001 Elsevier Science B.V. All rights reserved.