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.
In the present work, an improvement in light‐conversion efficiency by coating spherical particles of mesoporous TiO2 (MT) and copper‐modified mesoporous TiO2 (CMT) on single‐crystalline Si solar PV cell is observed. The studies are carried out by spin coating with different concentrations of MT (0.25 to 1.5%) and CMT (0.25 to 1.0%) particles on bare cells independently and compared with a bare solar cell throughout the work. It is observed that in the case of MT coatings, the conversion efficiency increases initially and reaches a maximum of 9.77% at a coating concentration of 1.0%; thereafter, it decreases with an increase in coating concentration. This decrease in efficiency may be attributed to coagulation of MT particles, whereas in the case of CMT particles the conversion efficiency reached a maximum of 8.85% at 0.5% concentration and decreases thereafter. This study indicates that a higher efficiency can be achieved at lower concentrations of CMT coating compared to MT coatings on a bare solar cell. The increase in efficiency may be attributed to better surface passivation and/or trapping of electrons at the metal sites by Cu in CMT. Recombination lifetime measurements results corroborated that CMT particles show better surface passivation as a result of which there is an increase in efficiency. Diffused reflectance and short‐circuit current ratio versus wavelength studies on MT and CMT also revealed that CMT particles perform better than MT particles.
Designing the low-cost, earth-abundant, and non-precious catalysts for electrochemical water oxidation reaction is particularly important for accelerating the development of sustainable energy sources and further can be fed to the fuel cells. In the present work, we report the oxygen evolution reaction (OER) activity of a metal-oxide catalyst, Mn3O4, and studied the effect of transition metal doping (Cu and Fe) on the OER activity of Mn3O4 in the alkaline medium. The catalysts, Mn3O4, and transition-metal (Cu and Fe) doped Mn3O4 were prepared using the hydrothermal reaction technique. The powder X-ray diffraction studies revealed that these compounds are adopting the tetragonal Spinel structure with I41/amd space group and further supported with FTIR spectroscopic measurements. These results were further supported by high-resolution transmission electron microscopic measurements. The electrochemical measurements on these catalysts reveal that the transition-metal (Cu and Fe) doped Mn3O4 catalysts show better OER activity than the pristine Mn3O4. The transition-metal (Cu and Fe) doped Mn3O4 catalysts exhibit the lower overpotential for OER (MCO = 300 mV and MFO = 240 mV) than the pristine Mn3O4 (MO = 350 mV) catalyst. The better performance of Fe doped Mn3O4 was further supported by turnover frequency (TOF) calculations.
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