The purpose of this study is to verify the possibility of applying alumina (Al2O3) as the passivation and antireflective coating in silicon solar cells.
Model of a studied structure contains the following layers: Al2O3/n+/n-type Si/p+/Al2O3. Optical parameters of the aluminium oxide films on silicon wafers were measured in the range of wavelengths from 250 to 1,400 nm with a spectrophotometer Perkin Elmer Lambda 900. The minority carrier lifetime at the start of the n-type Si base material and after each of the next technological process was analysed by a quasi-steady-state photoconductance technique. The electrical parameters of the solar cells fabricated with four different thickness of the Al2O3 layer were determined on the basis of the current-voltage (I-V) characteristics. The silicon solar cells of 25 cm2 area and 300 µm thickness were investigated.
The optimum thickness of alumina as passivation layer is 90 nm. However, considering also antireflective properties of the first layer of a photovoltaic cell, the best structure is silicon with alumina passivation layer of 30 nm thickness and with TiO2 antireflective coatings of 60 nm thickness. Such solution has allowed to produce the cells with the fill factor of 0.77 and open circuit voltage of 618 mV.
Measurements confirmed the possibility of applying the Al2O3 as a passivation and antireflective coating (obtained by atomic layer deposition method) for improving the efficiency of solar cells.
