Indium-tin-oxide (ITO) layers were deposited on n-Si(111) (resistivity rho > 1000 Omega cm) by RF magnetron sputtering, and the effects of sputtering pressure (P) and temperature (T-S) on their electrical properties and transmittance spectra were investigated. The electrical conductivity sigma of ITO layers reached a maximal of 1.6 x 10(4) S cm(-1) at T-S = 370 degrees C and P = 1.0 Pa. The transmittance spectra of the ITO layers changed significantly depending on P and T-S. We next employed ITO layers as the front contact for p-BaSi2(20 nm)/n-Si(111) (rho = 1-4 Omega cm) heterojunction solar cells, and investigated the influence of the P and T-S on their performance. The energy conversion efficiency reached a maximum (eta = 6.6%) at P = 1.0 Pa and T-S = RT and 90 degrees C, differently from the TS suitable for ITO films directly on a Si(111) substrate. Deep level transient spectroscopy revealed the presence of defects in the p-BaSi2 side close to the p-BaSi2/n-Si interface, located at 0.16 eV from the conduction band minimum, when sputtered at 230 degrees C. (c) 2020 The Japan Society of Applied Physics