Efficiency Enhancement of c-Si/TiO$_2$ Heterojunction Thin Film Solar Cell Using Hybrid Metal-Dielectric Nanostructures

Abstract

The hybrid metal-dielectric nanostructures (HMDN) are promising candidates to address the ohmic loss by conventional nanostructures in photovoltaic applications by strong confinement and high scattering directivity. In this study, we present a c-Si/TiO$_2$ heterojunction thin film solar cell (TFSC) where a pair of triangular HMDN comprised of Ag and AZO was utilized to enhance the longer wavelength light absorption. The presence of the TiO$_2$ inverted pyramid layer, in combination with the ITO and SiO$_2$-based pyramid layers at the front, enhanced the shorter wavelength light absorption by increasing the optical path and facilitating the coupling of incoming light in photonic mode. Consequently, the average absorption by 1000 nm thick photoactive layer reached 83.32 % for AM 1.5G within the wavelength range of 300 - 1100 nm which was investigated by employing the finite-difference time-domain (FDTD) method. The electric field profile and current density profile demonstrated the respective contributions of each layer in the absorption of light at shorter and longer wavelengths. The structure exhibited a short circuit current density ($J_{sc}$) of 37.96 mA/cm$^2$ and a power conversion efficiency ($PCE$) of 17.42 %. The efficiency of our proposed structure experienced a maximum relative change of 0.34 % when a polarized light was exposed with an angle of 0$^\circ$ to 90$^\circ$. The incorporation of self-heating in non-isothermal conditions reduced $PCE$ by $13.77 \%$. In addition, the comparative analysis to assess the impact of HMDN on our structure revealed a $4.54 \%$ increase in $PCE$ of the structure with metallic nanostructures, paving the way for the utilization of HMDN to enhance the performance of TFSC.