Over the last two decades, Dye Sensitized Solar Cell (DSSC) has been emerging as an alternative to conventional silicon photovoltaic devices because of its low cost, abundant raw material, facile fabrication process, efficient photovoltaic performance and stability. For becoming a potential candidate to replace traditional solar cells, DSSC has to undergo a lot of challenges in enhancing the device performance, one of the key role, for which, is being played by the photoanode material.TiO2 (Titanium dioxide) nanoparticle ﬁlms have been used widely for DSSC since the electron injection rates from the excited dye into the TiO2 nanoparticles are ultra-fast, in the order of femto seconds, but due to low electron mobility, the electron recombination rates are high.
SnO2 (Tin dioxide) on the other hand is a promising oxide material because of its higher electronic mobility and large band gap. Mobility reported in both single crystal SnO2 as well as nanostructures are orders of magnitude higher than in ita competitor TiO2. Furthermore, SnO2 has a low sensitivity to UV degradation due to its larger band gap, and hence has better long term stability. Presently, I am carrying out different projects in fabricating DSSC with SnO2 photoanodes.For one project, we are investigating the performance of DSSC with photoanodes made from self-prepared paste using SnO2 nanoparticles, Fluorine doped SnO2 nanoparticles and composite systems of nanoparticles and graphene sheets provided from our collaborators in Berlin. For the other project I am preparing photoanodes made from self-prepared paste using commercial nanoparticles of SnO2.We investigate the performance of DSSC fabricated with pre-treatment with TiCl4 and TiOx precursor solution separately to form a blocking layer between the FTO layer and electrolyte to inhibit electron recombination from FTO to the elctrolyte.We also post treat our SnO2 photoanodes with both TiCl4 and TiOx precursor solution separately to passivate the SnO2 anode layer with titania layer and reduce recombination from the photoanode to the electrolyte.The pre-treatment and post treatment of SnO2 as a photoanode can improve the Voc, which is necessary since the conduction band minima of SnO2 is located below that of TiO2 and in turn decides a low Voc(open circuit voltage) in SnO2 anode DSSC. We furthermore study the performance of the cells with the introduction of graphene and Multi Walled Carbon NanoTubes (MWCNT) which provide a directed path for electron transport within the photoanode and increase the current density in the device. However the presence of these carbon materials decreases the Voc due to their energy band structure, but the increase of current can largely compensate the decrease in Voc, and result in a better performing solar cell. The crystallinity of the nanoparticles, pre and post treatment of photoanode and the presence of graphene and MWCNT influence the functional properties of the solar cells, and call for optimization of the photoanode to maximize the photo conversion efficiency.
M.Tech. in Radio Physics and Electronics
University College of Science and Technology, University of Calcutta.
Dissertation- “Design and Simulation of Piezoelectrically Actuated MEMS based valveless diffuser micropump” carried out at Indian Institute of Technology(IIT), Kharagpur.