• Energy Research

Abstract Quantum efficiency and impedance spectroscopy tools are employed for understanding the influence of parasitic absorption losses and partial field effect surface passivation by the silver nanoparticles (Ag NPs) on electrical properties of textured silicon solar cells without and with Si3N4 spacer layer. The parasitic absorption losses from Ag NPs reduced the internal quantum efficiency near the surface plasmon resonance region. The passive components like; series and parallel resistances, chemical capacitance of solar cells without and with Ag NPs are estimated after fitting impedance semicircles, which are further used for estimating effective carrier lifetime (τeff) values. Under AM1.5G illumination, cells with Si3N4 spacer layer showed a large decrease in the τeff due to the strong parasitic absorption losses from the Ag NPs. But, the cells without Si3N4 spacer layer showed a small decrease in the τeff due to the reduced surface recombination after partial field effect passivation from near-fields of Ag NPs’ surface plasmon resonances on the emitter surface.

Abstract Gold nanoparticles (GNPs) of various sizes (range of 5–85 nm) were synthesized and various concentrations (range of 0.1–0.7 wt%) were blended with TiO 2 nanopowder for fabricating conformal TiO 2 –Au nanocomposite (NC) films. In optical and electrical studies, we have observed that GNPs of sizes in the range of 15–40 nm, and concentrations in the range of 0.1–0.25 wt% offer the maximum enhancement in dye-sensitized solar cell (DSSC) performance due to the enhanced near-field excitation of dye molecules along with incident light far-field. The best plasmonic DSSC performance was observed with 0.24 wt% of ∼36 nm GNPs with an enhancement of 18.44% in photocurrent. Despite the strong absorptance with ∼5 nm GNPs, only a modest improvement in photovoltaic behavior was observed due to plasmonic heating effects of strongly localized near-fields instead of dye molecules excitation. With ∼85 nm GNPs, we have observed minimal enhancement in device performance due to large scattering cross-sections, which result in the incident energy to be sent back to the far-field after interacting with GNPs instead of localizing around them. The optimized size and concentration of GNPs were also used for fabricating high efficiency DSSCs using commercial TiO 2 paste and two different dyes (N719 and N749) in order to study the effects of apparent extinction coefficients of the dyes as well as device thickness on photocurrent and energy conversion efficiency enhancements of DSSCs.

Silicon solar cells with different front texturization are used for understanding pyramidal size influence on plasmonic light trapping. Cells with different pyramidal heights and widths have shown strong light back scattering in the surface plasmon resonance (SPR) region and minimal light forward scattering in the off-resonance region of silver nanoparticles (NPs). On the other hand, cell surface with similar pyramidal heights and widths has shown reduced back scattering in the SPR region, as well as enhanced light forward scattering in the off-resonance region of NPs with good optical impedance matching. The reason for these types of light interaction with NPs (nanoscale) and textured silicon (micrometer-scale) is explained, and plasmonic textured silicon solar cell performance with different pyramidal sizes using quantum efficiency measurements is verified.