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The effect of composition on the optical absorption and photoluminescence (PL) spectra of the semiconductor quantum dots (QDs) of CdSxSe1-xembedded in borosilicate glass matrix has been studied. It is observed that the first exciton absorption peak shifts from 2.62 to 2.21 eV and the PL peak shifts from 2.16 to 1.87 eV as the composition of selenium increases from 8 to 92 wt%. Samples having higher concentration of sulfur are found to have higher PL peak intensity, which is interpreted to be due to high concentration of shallow traps in the sulfur-rich samples. Absorption coefficient goes on increasing as the selenium content increases. This may be attributed to the fact that selenium has higher atomic size as compared to that of sulfur.

Two-photon optical nonlinear absorption has been studied in quantum dots of CdSxSe1-xgrown in borosilicate glass matrix by two-step annealing technique. Femtosecond laser and open aperture Z-scan technique has been used for measuring the third-order nonlinear two-photon absorption coefficient (β(3)). Only the third-order and not the fifth-order nonlinear effects are observed at low intensities (1.6–3.2 GW cm-2) of laser used in the present experiment. At such low intensities, the variation of β(3)is found to be almost intensity-independent. For a given annealing duration of the quantum dots, the value of β(3)is found to be higher for sulfur-rich samples as compared to that for selenium-rich samples. This is attributed to the presence of shallow traps formed due to sulfur vacancies in the sulfur-rich samples. Further, the value of β(3)increases with the increase in the size of quantum dots and the rate of increase of β(3)with the increase of average radius is found to be higher for sulfur-rich samples.

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Crystalline silicon solar cells have been the workhorse of the Solar Photovoltaic industry, contributing to >90% of the total installations. The fabrication of solar cells involves multi-process steps i.e. chemical treatment, diffusion, passivation and metallization. Among these process steps of solar cell manufacturing, metallization is the most critical one since it not only influences cell performance but also the cost of manufacturing to a great extent. A proper metallization process essentially helps in reduction of various electrical and optical losses. A lot of research is being carried out on various metallization technologies to arrive at an efficient, cost-effective solution for contact formation. Screen printing, flexographic printing, laser metal sintering and recently developed 3D printing are some of the technologies of interest in this field. While 3D printing, laser metal sintering, etc. are still at lab level, flexographic and gravure printing are in search of a suitable paste which can make the technology production-worthy. It is the screen-printed technology of solar cells that currently dominates the commercial market because of its low production cost and process simplicity. Amongst the several technologies that have been developed till date for cell metallization, the screen-printing technology promises to be the most reliable, rugged and production-worthy technology. In this paper, different metallization technologies viz. screen printing (conventional, knotless), stencil printing, light induced plating, metal sintering, flexographic printing, aerosol printing etc. used for contact formation in high efficiency silicon solar cells have been reviewed.