Characterization and optimization of indium tin oxide films for heterojunction solar cells

Well suited and reliable values of the optical and electrical properties of thin indium tin oxide (ITO) films are needed in order to choose the optimal deposition parameters and to perform reliable modeling for solar cells design. In this work, a new method will be presented to evaluate the ITO transparency directly on silicon substrates. The effects of each deposition parameter that influences the ITO transparency and conductivity force a trade-off in the frame of values useful for SHJ solar cells. The deposition of our optimized ITO film on a textured wafer yields a weighted average reflectance as low as 4.4 +/- 0.2%. The deposition of an MgF(2)/ITO double-layer anti-reflection coating (DL-ARC) on textured cells increases the efficiency from 17.9%, measured immediately after contacts have been added to the ITO, to 18.4% after the MgF(2) deposition. An annealing step at 200 degrees C for 10 min proved to further increase the efficiency up to 18.9%, for a total gain of 1%. (C) 2011 Elsevier B.V. All rights reserved.