ITO distributed Bragg reflectors fabricated at low temperature for light-trapping in thin-film solar cells

A high performance distributed Bragg reflector (DBR) fabricated using the single indium tin oxide (ITO) material is proposed for light trapping in thin-film solar cells. The large index contrast of the ITO DBRs was obtained by depositing alternating layers of dense ITO films and porous ITO films. The high refractive index of the dense ITO films was achieved by long-throw radio-frequency magnetron sputtering technique at room temperature. On the other hand, the porous ITO films with low refractive index were formed by applying supercritical CO2 (SCCO2) treatment at 60°C on gel-coated ITO thin films. Porous structures were obtained with the SCCO2 treatment to volatilize or extract organic matters from the films. The index contrast of the ITO bilayers was higher than 0.5 at blue and green spectral ranges. In addition, small deviations on the optical thickness of the ITO bilayers were observed during the DBR stacking processes. For the DBR comprising 4 periods ITO bilayers, the reflectance and sheet resistance of 87.9% and 35Ω/□ were achieved at 426nm. The reflectance spectra and electrical characteristics of the conductive DBRs fabricated at low temperature. [Display omitted] •A conductive DBR electrode fabricated using the single ITO material is proposed.•The DBRs were formed by stacking dense and porous ITO bilayers at low temperatures.•The index contrast of the ITO bilayer was higher than 0.5 at blue and green spectral ranges.•The Bragg reflectivity and sheet resistance of 87.9% at 426nm and 35Ω/□ were obtained.