AlOx/(p(+)nn(+))Cz-Si/IFO and ITO/AlOx/(p(+)nn(+))Cz-Si/IFO solar cell structures have been fabricated from n-type Czochralski (Cz) silicon wafers through boron and phosphorus diffusion for producing the p(+)-Si emitter and n(+)-Si layer, respectively. The In2O3:F (IFO), AlOx, and In2O3:Sn (ITO) films have been grown by ultrasonic spray pyrolysis at 475 degrees C, 330 degrees C, and 375 degrees C, respectively. The AlOx film thickness was varied in the range 27-108 nm, the annealing time at 330 degrees C in an Ar 5% O-2 atmosphere containing vapor of a 2 M H2O solution in methanol - in the range 0-18 min, and the sheet resistance of the p(+)-Si emitter - in the range 28-133 Omega/square (varied through layer-by-layer chemical etching). We have studied the internal quantum efficiency (IQE) spectrum, photocurrent J(IQE) of the structures (evaluated from the IQE spectrum), as well as their photovoltage and pseudo-fill factor evaluated from Suns-V-oc measurements. The results demonstrate that the level of p(+)-Si surface passivation increases with increasing AlOx film thickness and as a result of annealing. The optimal sheet resistance of the emitter is similar to 65 Omega/square. The pseudo-efficiency of the optimized ITO/AlOx/(p(+)nn(+))Cz-Si/IFO structures was 20.2% under front illumination. (C) 2013 Elsevier Ltd. All rights reserved.