Abstract :

The continuous and reliable supply of energy is essential for the development and economic growth of a country. Fossil fuels based conventional energy sources are still considered as the main source of energy. But limited availability, environmental issues and increasing demand of energy have motivated the researchers and scientist toward renewable energy sources. Sun is one of the main source of renewable energy and solar energy may be harnessed directly or indirectly to produce energy. Several photovoltaic conversion technologies are used to convert solar radiation into electricity. Amongst them Dye-sensitized solar cells (DSSCs), classified as third-generation solar cells, are promising and low-cost photovoltaic technology.
In the reported research dye sensitized solar cell are realized with a focus on performance and functionality enhancement by using new dyes and modifying the properties of counter electrode materials. DSSCs are fabricated by using MnO₂ as a coating material for counter electrode replacing commercially available and widely used Platinum coated electrodes. The overall performance of solar cell has been improved by doping MnO₂ with silver (Ag). In addition to this, Solar cells are realized by using dyes extracted from natural sources. The effect of co-sensitization from mixture of natural dyes is also evaluated. Moreover, efforts are made to reduce the cost and improve the overall performance of DSSC by incorporating battery cells waste in semiconductor binder layer of titanium dioxide (TiO2).
The characteristics of dyes and electrodes are investigated by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Cyclic voltammetry (CV). Photovoltaic performance of solar cells is evaluated by current-voltage (I-V) characteristics in dark and illumination under 1 sun. In order to study charge transport mechanism, detailed impedance spectroscopy studies are performed to study frequency and voltage dependent capacitance (C-V-f), resistance(R-V-f) and impedance (Z-f) characteristics.
The performance of solar cells is evaluated by comparing the obtained results with the solar cells fabricated from commercially available N3, N719 and SQ2 Ruthenium dyes. The trends of photovoltaic behavior and impedance characteristics are in agreement with commercial dyes DSSCs. Effect of co-sensitization on the performance of DSSCs with metallic (N3, N719) and organic (SQ2) dyes is also investigated.
DSSCs fabricated from natural dyes demonstrated photovoltaic conversion but power conversion is less (< 1% ). However, DSSCs co-sensitized with mixture of dyes demonstrated improved performance than DSSCs fabricated using only one dye. Enhancement in efficiency is achieved in solar cells realized with silver(Ag) doped MnO2 coated counter electrodes. The electrochemical studies of Ag- MnO₂ revealed better electro catalytic activity and lower charge transfer resistance (Rct) than pristine MnO₂-based counter electrode. DSSC fabricated with Ag-MnO₂ CE demonstrated improved PCE of 3.02% with Voc and Jsc of 0.66V and 13.3 mA/cm2 respectively. DSSCs prepared of counter electrodes from battery cells waste with and without semiconductor binder (TiO2) yield the efficiencies of 2.44 % and 1.80%. DSSCs with counter electrodes without TiO2 binder can prove to be an ecofriendly, low cost solution for counter electrode with easy synthesis processes. Results obtained from these studies yield that DSSC can be realized in a number of ways to enhance the efficiency and minimize the overall cost.