Low temperature characteristic of ITO/SiOx/c-Si heterojunction solar cell

Based on the temperature-dependent measurements and the numerical calculation, the temperature response of the photovoltaic parameters for a ITO/SiOx/c-Si heterojunction solar cell have been investigated in the ascending sorting of 10-300 K. Under unique energy concentrated photon irradiation with the wavelength of 405 nm and power density of 667 mW cm(-2), it was found that the short-circuit current (I-SC) was nonlinearly increased and the open-circuit voltage (V-OC) decreased with temperature. The good passivation of the ITO/c-Si interface by a concomitant SiOx buffer layer leads to the rare recombination of carriers in the intermediate region. The inversion layer model indicated that the band gap of c-silicon was narrowed and the Fermi level of n-type silicon (E-F(n)) tended to that of the intrinsic Fermi level (E-F(i)) (in the middle of band gap) with the increase of the temperature, which lessened the built-in voltage (VD) and thus the V-OC. However, the reduction by 90% of V-OC is attributed to the shift of E-F(n) in c-silicon rather than the energy band narrowing. Through the analysis of the current-voltage relationship and the data fitting, we infer that the series resistance (R-s) is not responsible for the increase of I-SC, but the absorption coefficient and the depletion-width of c-silicon are the causes of the enhancing I-SC. Mostly, the interaction of the photon-generated excess 'cold hole' and the acoustic phonon in n-Si would influence the variation of Iph or ISC with temperature.