Papers by Keyword: Photovoltaic Performance

Abstract: Thermal and photo instabilities are two major issues for organic-inorganic lead halide perovskite solar cells. Mixing of A site cations and X cite halogens are tried to address these issues, but the performance is still not reached the theoretical Shockley Quissier limit. One of the reasons for this is the energy loss ratio with band gap energy. Despite the high open circuit voltage, this ratio is lower for perovskite solar cell in competition with silicon technology. Open circuit voltage can be increased by different ways, but short circuit current is compromised. To increase open circuit voltage without affecting the short circuit current is the surface passivation technique. Numerous studies have been conducted on electron transport layer and perovskite interface, with a very few on hole transport layer and perovskite interface. Both interfaces are equally important. Here we passivated the later interface by inserting a 10 nm thick layer of caesium-formamide based lead mixed halide perovskite in FAMA mixed perovskite solar cell. Our proposed model achieved an efficiency of 31.42 % with a high fill factor of 86.4 %. At the same time, we recorded higher open circuit voltage of 1.46 V and 25.49 mA/cm² short circuit current. Our proposed model will help in experimental work for making highly efficient perovskite solar cells.

Abstract: Over the past few years, metal halide perovskites have been considered as a promising material for application in photovoltaic devices because of its unique optical and electrical properties. In particular, Sn-based perovskites have been being considered to replace Pb-based perovskite because of the Pb toxicity that will raise serious concerns on the environmental issue. In this report, we present our attempt to synthesize the Sn-based perovskite (namely, Cs₂SnI₆), which is air and thermal stable, and use it as an electron transport layer in dye-sensitized solar cells (DSSC) for improving its power conversion efficiency. The synthesize of Cs₂SnI₆ perovskite was done by mixing Cs₂CO₃ in HI and SnI₄ in ethanol to form a precipitate at room temperature. The purification process was an important part to collect effectively the synthesis product. The fabrication of DSSC was done by a standard process based on the screen printing and spin-coating techniques, while the characterization of Cs₂SnI₆ was done by UV-Vis spectroscopy and XRD measurement. In the present experiment, the addition of the Cs₂SnI₆ layer was performed by spin coating the Cs₂SnI₆ solution onto the TiO₂ mesoporous layer. The photovoltaic performance of the fabricated DSSC shows a significant enhancement in the short circuit photocurrent density (J_sc) and conversion efficiency, that is, from 15.04 mA/cm² to 16.33 mA/cm² from 5.7% to 6.75% due to the incorporation of spin-coated 5 mM Cs₂SnI₆ in comparison to the reference cell without Cs₂SnI₆.

Abstract: Dye-sensitized solar cells based on Y-doped TiO₂ thin film prepared by the hydrothermal method show a photovoltaic efficiency of 5.11%, which is higher than that of the undoped TiO₂ thin film (4.72%). The Y-doped films exhibit an elevated electron Fermi level,which may enhance band bending to lower the density of empty trap states.Because of this Y-doping, the Dsscs can alleviate the decay of light to electric energy conversion efficiency due to light intensity reduction.

Abstract: ZnO nanorod arrays were successfully prepared by chemical bath deposition (CBD) and hydrothermal method (HTM), respectively. The photovoltaic performance of ZnO nanoarrays as photoelectrodes in dye-sensitized solar cells (DSCs) was investigated. Experimental results show that ZnO seed crystals prepared by a sol-gol process have c axis orientation and consist of nanoparticles within the range of 50~100nm. The same particle size and orientation is well preserved in ZnO nanoarrays grown on the seed crystal layers. The photovoltaic performance of DSCs based on ZnO nanoarrays as the photoelectrodes is poor, due to the weaker adsorption bond force between ZnO and dye, and lower dye adsorption quantity. By contrast, the DSCs composed of ZnO arrays prepared by hydrothermal method have optimal performance, the corresponding short circuit photocurrent density (J_sc), open circuit voltage (V_oc), fill factor (FF) and photoelectric conversion efficiency (η) are 4.89 mA/cm², 0.650V, 0.39 and 1.25 %, respectively.

Abstract: Graphene nanosheets (GNs) were introduced into graphite counter electrode to construct a graphite/GNs (GGN) counter electrode to enhance the photovoltaic properties of the dye–sensitized solar cells (DSCs). The efficiency of the DSCs with the GGN electrode is 38.4% higher than that of DSCs with graphite electrode. The improved efficiency is attributed to the enhancement in the short circuit photocurrent density and fill factor. The GNs with high conductivity in the GGN electrode are believed to strengthen the contacts among the graphite particles as well as between the carbon film and the substrate, providing enough conductive paths for the transportation of the electrons in the electrode. Therefore, the sheet resistance of the GGN electrode is reduced and the catalytic activity for triiodide ( ) reduction is improved, which are two factors to enhance the efficiency of the cell.

Abstract: In order to understand the influence of morphology of vacuum-evaporated conjugated organic thin film on organic photovoltaic performance, oligothiophene derivatives, 2,3,4,5-tetrathienylthiophene (X-5T) and 2,5-dithienyl-3,4-di ((2,2') bithiophene-5yl) thiophene (X-7T), were prepared. The thermal behaviour and morphologies of vacuum-deposited X-5T and X-7T films were examined by differential scanning calorimetry (DSC) and x-ray diffraction (XRD). The influence of morphologies of vacuum-evaporated X-5T and X-7T films on organic photovoltaic performance was hen investigated. It was found that vacuum-evaporated oligothiophene derivative films possessing crystalline morphology could be beneficial to improve organic photovoltaic performance of device by promoting forward interfacial electron transfer and transport.

Abstract: Dye-sensitized solar cells based on Zn-doped TiO₂ thin film prepared by the hydrothermal method show a photovoltaic efficiency of 7.68%, which is higher than that of the undoped TiO₂ thin film (6.16%). The Zn-doped films exhibit an elevated electron Fermi level,which may enhance band bending to lower the density of empty trap states.Because of this Zn-doping,the consequent Dsscs can alleviate the decay of light to electric energy conversion efficiency due to light intensity reduction. Intensity-modulated photocurrent spectroscopic analysis reveals that enhanced transport of photogenerated electrons as a result of the trap density minimization is responsible for the high photovoltaic performance.

Abstract: Mesoporous carbon (MC) materials with surface area of 400 m²g^-1 were prepared and incorporated into the polymer gel electrolyte comprising of polyvinylidene fluoride and 1-methyl-3-hexylimidazolium iodide to fabricate the composite gel electrolytes. The photovoltaic performance of the quasi-solid-state dye-sensitized solar cells was improved through incorporating MC into electrolyte. The dye-sensitized solar cell with composite gel electrolyte containing 3 wt% MC achieved the best photovoltaic performance, and the corresponding open-circuit voltage, short-circuit current density, fill factor and overall conversion efficiency were 0.59V, 13.22 mAcm^-2, 0.66 and 5.15%, respectively. The stability of dye-sensitized solar cells with composite gel electrolyte was far superior to the cell with organic liquid electrolyte.

Abstract: Mesoporous carbon (MC) materials with wormhole-like mesopores were prepared and incorporated into the polymer gel electrolyte comprising of polyvinylidene fluoride and 1-methyl-3-hexylimidazolium iodide. These gel composites were employed as the electrolyte for quasi-solid-state dye-sensitized solar cells. The photovoltaic performance of the quasi-solid-state dye-sensitized solar cells improved through incorporating MC into electrolyte. The dye-sensitized solar cell with composite gel electrolyte containing 3 wt% MC achieved the best photovoltaic performance, and the corresponding open-circuit voltage, short-circuit current density, fill factor and overall conversion efficiency were 0.59V, 13.22 mAcm-2, 0.66 and 5.15%, respectively. The stability of dye-sensitized solar cells with composite gel electrolyte was found to be far superior to the cell with organic liquid electrolyte.

Abstract: Poly(vinylidene fluoride)(PVDF) is photochemically stable even in the presence of TiO2 and Pt nanoparticles, and poly(methacrylate)(PMMA) has good solvent retention. The quasi-solid electrolytes based on PVDF-PMMA blend polymer were prepared in this work by soaking a porous membrane in an organic electrolyte solution containing the I−/I3− redox couple. The as-prepared electrolytes were characterized by means of Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope respectively. Moreover, the conductivity and the voltage-current curves of the electrolytes were measured by electrochemical workstation. The results indicated that the optimum blend proportion of PVDF and PMMA was 6:4. The porous structure prepared with the addition of propanetriol was beneficial to ion diffusion and thus enhanced the conductivity of the electrolytes. The gel polymer electrolyte had a conductivity of 0.14 mS•cm-1 under the ambient atmosphere. Furthermore, electrolytes were assembled to fabricate DSSCs and the performance of the cells was tested. The good properties with the open-circuit voltage of 0.60V and the short-circuit current of 1.1mAcm-2 were achieved upon illumination with visible light.