Hydrogenated nanocrystalline silicon films were prepared by hot-wire method at low substrate temperature (200∘C) without hydrogen dilution of silane (SiH4). A variety of techniques, including Raman spectroscopy, low angle X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and UV-visible (UV-Vis) spectroscopy, were used to characterize these films for structural and optical properties. Films are grown at reasonably high deposition rates (>15 Å/s), which are very much appreciated for the fabrication of cost effective devices. Different crystalline fractions (from 2.5% to 63%) and crystallite size (3.6–6.0 nm) can be achieved by controlling the process pressure. It is observed that with increase in process pressure, the hydrogen bonding in the films shifts from Si–H to Si–H2and(Si–H2)ncomplexes. The band gaps of the films are found in the range 1.83–2.11 eV, whereas the hydrogen content remains <9 at.% over the entire range of process pressure studied. The ease of depositing films with tunable band gap is useful for fabrication of tandem solar cells. A correlation between structural and optical properties has been found and discussed in detail.

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Dye-sensitized solar cells (DSSCs) are fabricated based on rutile TiO 2 microspheres that are synthesized by a hydrothermal route. We found that, with increasing deposition time, semi microspheres get converted into microspheres. Our results show that the TiO 2 -based cells exhibit a noticeable improvement in the overall efficiency: maximum 3.81% versus 0.67% for the reference cell made of a rutile TiO 2 semispherical nanocrystalline film. This extraordinary result is attributed to the effective light trapping and dye loading resulting in the highest efficiency 3.81%.

Various measurements and experiments are performed to establish the mechanism of passivation on emitter and base of conventionally manufactured solar cell with p-type base. The surface coatings on the emitter are removed. The bare surface is then coated with silicon (Si) nanoparticles (NPs) with oxygen termination. It shows an increase in the cell efficiency up to 14% over bare surface of solar cell. The NPs show enhancement in light scattering from the surface, but shows an increase in the recombination lifetime indicating an improved passivation. When back contact is partially removed, the coating on bare back side ( p-type) of the solar cell also improves the cell efficiency. This is also attributable to the increased recombination lifetime from the measurements. Same NPs are seen to degrade the surface of n and p-type Si wafers. This apparently contradictory behaviour is explained by studying and comparing the emitter (n-type) surface of the solar cell with that of n-type Si wafer and the back surface ( p-type) with that of p-type Si wafer. The emitter surface is distinctly different from the n-type wafer because of the shallow p-n junction causing the surface depletion. Back surface has aluminium (Al) metal trace, which plays an important role in forming complexes with the oxygen-terminated Si NPs (Si-O NPs). With these studies, it is observed that increase in the efficiency can potentially reduce the thermal budget in solar cell preparation.