Sumita Mukhopadhyay

Sol–gel synthesized mesoporous anatase titanium dioxide nanoparticles for dye sensitized solar cell (DSSC) applications

Hierarchically structured titanium dioxide nanoparticles were successfully synthesized by the sol–gel method. The synthesized nanoparticles were subjected to powder X-ray diffraction, UV–Vis DRS spectroscopy, Brunauer–Emmett–Teller method, Barrett–Joyner–Halenda analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. The powder X-ray diffraction pattern shows that the obtained particles are of anatase phase with good crystallite nature. The nitrogen adsorption and desorption isotherms show that the prepared material has surface area of 31.71 m2 g−1 and the pore size distribution analysis shows the average pore diameters of mesoporous TiO2 nanostructures to be 7.1 and 9.3 nm. The UV–Vis DRS spectrum shows that the TiO2 nanoparticles are having absorption in the ultraviolet region. The optical band gap of the nanoparticles is 3.2 eV. The morphological studies show the morphology of the particles as spherical in shape. The elemental compositions of TiO2 nanoparticles were confirmed by energy-dispersive X-ray spectrum analysis. The conversion efficiency of the solar cell was 3.415% with open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) of 0.607 V, 13.206 mA cm−2 and 42.56%, respectively.

Development of n-type microcrystalline SiOx:H films and its application by innovative way to improve the performance of single junction µc-Si:H solar cell

Light trapping is one of the fundamental necessities of thin film based solar cell for its performance elevation. Back reflection of unused light of first pass is the key way to improve the light trapping phenomena. In this study we have reported the development of n-type hydrogenated microcrystalline silicon oxide (n-µc-SiO:H) layers of different characteristics. The deposition has been done by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. The detailed characterization of the films include the following: (1) electrical properties (2) optical properties like E04 (3) structural studies which include crystalline fraction by Raman spectroscopy and grain size by X-ray diffraction measurement, FTIR spectroscopy, AFM and TEM studies. n-µc-SiO:H layer has been introduced as the n-layer of single junction p–i–n structure µc-Si solar cells. By various techniques the optimum use of n-µc-SiO:H layer for enhancing the performance of µc-Si:H solar cells has been done. It has been found that by using suitable bilayer of two different n-µc-SiO:H layers, it is possible to increase the solar cell performances. The maximum efficiency obtained without any back reflector is 8.44% that is about 8.9% higher than that obtained by using n-µc-Si:H layer as n-layer in the solar cells.

Nanorods and nanoparticles of titanium dioxide and their use in dye sensitized solar cells

Mesoporous TiO2 nanorods/nanorods were successfully synthesized by hydrothermal process at 170 °C for 72 hr. The powder X-ray diffraction pattern shows large fraction of anatase phase with good crystalline behavior of the prepared materials. The specific surface area and pore volume of the synthesized material are about 84.83 m2/g and 0.1316 cc/g respectively. The morphological results show that the TiO2 nanorods had diameter of ~ 25 nm and the length of ~ 80 nm. The nanoparticles have 20 nm in size. The current-voltage curve shows that the synthesized TiO2 nanostructure results in 36.7 % higher solar cell efficiency than commercial P25.

Innovative Utilization of Improved n-doped μc-SiOx:H Films to Amplify the Performance of Micromorph Solar Cells

Due to in-situ deposition process doped SiOx material attracts the PV community as intermediate reflecting layer (IRL) for the less hazardous deposition process. Previously we have been shown that how to formulate a better quality SiOx layer using seeding technique. In this paper we have shown that how this superior quality material will be beneficial as IRL and improve the performance of micromorph solar cells. Enhanced performance is observed when SiOx material is deposited with the help of highly conducting seed layer. For improving the performance of the micromorph solar cell further we have eliminated the n-layer of the top constituent cell. In the context of substituting the top n-layer, SiOx layer grown on seed layer is more significant as of its suitable optoelectronics properties. Initial efficiency of ∼12% is perceived in micromorph solar cells with the improved SiOx based IRL used innovatively which is 7.9% higher than that of the cell with conventionally developed and typical use of IRL.

Silicon heterojunction solar cells with novel fluorinated n-type nanocrystalline silicon oxide emitters on p-type crystalline silicon

A novel fluorinated phosphorus doped silicon oxide based nanocrystalline material have been used to prepare heterojunction solar cells on flat p-type crystalline silicon (c-Si) Czochralski (CZ) wafers. The n-type nc-SiO:F:H material were deposited by radio frequency plasma enhanced chemical vapor deposition. Deposited films were characterized in detail by using atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM), Raman, fourier transform infrared spectroscopy (FTIR) and optoelectronics properties have been studied using temperature dependent conductivity measurement, Ellipsometry, UV–vis spectrum analysis etc. It is observed that the cell fabricated with fluorinated silicon oxide emitter showing higher initial efficiency (η = 15.64%, Jsc = 32.10 mA/cm2, Voc = 0.630 V, FF = 0.77) for 1 cm2 cell area compare to conventional n-a-Si:H emitter (14.73%) on flat c-Si wafer. These results indicate that n type nc-SiO:F:H material is a promising candidate for heterojunction solar cell on p-type crystalline wafers. The high Jsc value is associated with excellent quantum efficiencies at short wavelengths (<500 nm).