• Energy Research

Abstract Polysulphide has proven to be an efficient electrolyte for QDSSC, but at the cost of corroding the counter electrode and degrading the sensitizer due to its high redox potential. In this view for the first time, we have used oxide nanoceramics as low cost, easily processable and highly porous solid-state electrolytes for QDSSCs. High residual porosity and formation of liquid phase nanodomains across grain boundaries have added advantages for adsorption and diffusion in these hole transport layer. Yttria stabilized zirconia and ceria co doped yttria stabilized zirconia are the two solid state electrolytes designed in place of polysulphide. Dopants namely Y3+ and Ce4+ in ZrO2 induces defects, oxygen vacancies and band shifts resulting in good charge transport. The interfaces and charge transfer kinetics suggests, recombination resistance offered by these ceramics avoid the back electron transfers via the downward shift of valence band (VB) much closer to that of sensitizer and also act as barriers (or passivation layer) to effectively suppress electron recombinations, resulting in high stability and Voc of the device. Devices designed with these new HTLs show efficiencies on par with polysulphide; they are extremely stable for almost up to 60 days (in ambient conditions), while cells fabricated with polysulphide electrolyte tend to degrade the device within 5 days.

Abstract Counter electrodes are critical components of third generation solar cells. A simple strategy of utilizing isostructural analogue of graphene, namely 2D molybdenum di-sulphide as nanohybrid with CuS as counter electrode is explored in this work. Formation of heterostructure photoanode with CdSe/CdS quantum dots along with nano-hybrid counter electrode has significantly boosted current density and open circuit voltage. The designed heterostructure and the counter electrode performs exceptionally well with good stability due to synergistic effect, thus spiking new hopes in achieving high efficiency in quantum dot solar cells.

Abstract Quantum dot sensitized solar cells (QDSSCs) can capably align with other emerging photovoltaic technologies, because of their ability to generate multiple excitons, availability of dynamic absorption ranges, and power conversion efficiency approaching 15% and beyond. Although the light-harvesting ability of these QDSSCs has increased dramatically, with EQE reaching up to 100%, charge carrier recombination has remained a major concern in retarding device performance and stability. The loss of charges within the semiconductor and across the photoanode interfaces has, to a large extent hindered device efficiency. As a result, it is critical to investigate an efficient and robust method of controlling charge recombination processes through thoughtful design. In this review, we summarize and offer insights into the most recent innovations with respect to design and construction of electron transport materials, with a focus on reducing recombination pathways via the dimensional nanostructures, carbon materials, and dopants; these being the three main strategies that have received much attention in recent years. The review also discusses and analyzes the solutions proposed by various researchers to overcome the challenges that restrict the electron transport in photoanodes of QDSSCs. Finally, the perspectives provide a) insights into choosing suitable materials, techniques and methods and also b) identifies and indicates potential areas that need attention or has scope for development.

This study demonstrates that the gasoline can be used as a co-solvent towards the modification of feedstock such as waste cooking oil for the synthesis of biodiesel via transesterification reaction, where the gasoline is removed from the reaction solution after the treatment. Parametric studies including varying the amount of co-solvent with respect to the feedstock, methanol/oil molar ratio, catalyst amount, reaction temperature, time, and stirring speed have been conducted to optimize the experiment. Our results show that biodiesel with a yield of ~ 99.4% is achieved at optimized conditions viz. 10% v/v co-solvent with respect to the feedstock, 0.6 wt% catalyst concentration, 6:1 molar-ratio, 50 °C temperature, 40 min reaction time, and 350 rpm stirring speed, while it is ~ 82.3% without the addition of co-solvent in the reaction solution under the same conditions. The thermodynamic parameters such as frequency factor, activation-energy, enthalpy, and entropy of the system have been estimated to be 1.3 × 104 min−1, 34.04 kJ mol−1, 31.48 kJ mol−1, and − 0.17 kJ mol−1 k−1, respectively. Further, various properties of the biodiesel produced with and without the feedstock modification have also been quantitatively measured and the developed approach favoured the feedstock modification towards improving the biodiesel yield and its physicochemical properties.

Abstract Atomic Force Microscopy has been used to study the nanoscale interaction between N719 dye and CdSe QDs/CdSe QDs and N719 dye on a TiO 2 surface in hybrid solar cells. The results of AFM study explains the factors like aggregation, linking and entrapment of sensitizers on TiO 2 surface. The photoresponse of nano sized materials in a hybrid solar cell consisting of mesoscopic TiO 2 , layers of N719 dye and CdSe quantum dots in sequential order has been reported in this paper. CdSe nanoparticles sandwiched between TiO 2 and N719 dye exhibited net power conversion efficiency of 1.16%. But the newly designed hybrid system where N719 dye anchored between TiO 2 and CdSe showed a good stability by delivering a power conversion efficiency of 2.64% with an improved open circuit potential and enhanced fill factor. In the cascade structure of TiO 2 /N719–CdSe, the re-organization of energy levels forms a stepwise structure, which is advantageous for an electron injection and hole-recovery in N719 dye and CdSe QDs respectively.

Abstract The future of third generation Quantum dot sensitized solar cells (QDSSCs) can be optimistic if concerns of charge recombination and stability of cells can be worked upon. In this work, we report the role of Graphene materials in its different dimension in overcoming recombination and enhancing power conversion efficiency (PCE). Composite of Graphene oxide nanoribbons (GNRs) synthesized by oxidative unzipping of multi walled carbon nanotubes (MWCNTs) was used as an effective electron transport layer with TiO2 as photo anode in QDSSCs. The best performing TiO2-GNR showed a significant enhancement in PCE of 3.7% for CdS based quantum dots, apart from increased efficiency reported earlier. Investigation of design of anode material reveals that the enhanced surface area and active sites of partially conducting GNRs facilitated uniform deposition of Titania particles (TiO2) with less aggregation, excellent mobility, presence of organic functional group for anchor of TiO2, its 1D quasi structure add to enhanced electron transport (less resistance).

This review presents recent advancements in high-voltage rechargeable aqueous batteries employing water-in-salt and modified water-in-salt electrolytes.