Realization of performance enhancement of thin film silicon solar cells by applying ITO/AZO bilayer TCO films as front electrode

Transparent conducting oxides (TCOs) are enormously endorsed as electrodes in solar photovoltaics industry due to featuring excellent opto-electronics properties. Indium tin oxide (ITO) has been quite popular in TCO industry as it features superior electrical conductivity along with higher optical transparency in comparison with other popular TCO materials. Nevertheless, the usage of ITO has been found to be limited as front electrodes in thin film silicon solar cells due to its sustainability issue in H 2 plasma and less abundance of indium. In contrast, other promising TCO materials such as aluminium doped zinc oxide (AZO), boron doped zinc oxide (BZO), gallium doped zinc oxide (GZO) etc. are found to quite durable in H 2 plasma environment and relatively cost-effective too. However, the opto-electronic qualities of such films are generally inferior to the ITO films. As a result, in this contribution, a thorough study has been carried out on relatively less explored ITO/AZO bilayer TCO films. A detailed comparison in terms of the structural, morphological and opto-electronic properties among single layer ITO films, single layer AZO films and ITO/AZO bilayer films has been made. The study has been further extended to realize the impact of using ITO/AZO bilayer films instead of single layer AZO film as front electrodes in single junction a-Si:H solar cells. The best single junction a-Si:H solar cell which featured ITO/AZO bilayer as front electrode and was fabricated into superstrate configuration demonstrated significant gain in short-circuit current density ( J sc ) of 0.79 mA/cm 2 and hence, power conversion efficiency of 0.37% (absolute) compared to the cells which comprised of single layer 900 nm thick AZO film as front electrode (reference cell). The improvement in J sc might be attributed to the realization of superior figure of merit (FOM) of bilayer samples to its counterpart.