Optimization of titanium dioxide decorated by graphene quantum dot as a light scattering layer for enhanced dye-sensitized solar cell performance

Titanium dioxide (TiO2) as a photoanode in dye-sensitized solar cells (DSSCs) has some drawbacks that reduce its photovoltaic performances i.e. low dye loading capacity and low light-harvesting efficiency. Therefore, TiO2 decorated by graphene quantum dot (GQD) as a light scatterer has been successfully fabricated via electrodeposition and drop-casting. The response surface methodology/central composite design was successfully utilized to optimize the preparation of photoanode with TiO2-GQD as a light scattering layer (LSL). A reduced quadratic model was successfully designed to predict the power conversion efficiency (PCE) accurately up to 97% with a 3% residual standard error. The TiO2-GQD LSL depicted a cluster of spherical nanoparticles on top of the photoanode that not only enhanced the light scattering effect but also improved the light-harvesting range from visible light to ultraviolet and near-infrared range. The resultant TiO2 nanoparticles with TiO2-GQD LSL showed vast enhancement of PCE up to 66% from 3.06% to 5.01% due to a good synergistic effect

Effect of electropolymerization potential on the properties of PEDOT/ZnO thin film composites

The physical, chemical and electrochemical properties of poly(3,4-ethylenedioxythiophene) /zinc oxide (PEDOT/ZnO) thin film electrode that were prepared electrochemically were studied. PEDOT was potentiostatically deposited on the hexagonal flake-like ZnO-covered ITO glass substrate by applying three different potentials (1.0 V, 1.25 V and 1.5 V) where under these circumstances, the effect of varying electropolymerization potentials where studied. The optical bandgap of each of the PEDOT/ZnO composites prepared were noticed to be within the range of 3.40 eV to 3.45 eV which were in between the optical band gap values of sole PEDOT and ZnO. The presence of both materials was asserted from XRD, FTIR and Raman analysis where all of the corresponding peaks for each of the materials in the spectra were assigned. SEM revealed the flake-like hexagonal morphology of ZnO which is in agreement with the XRD analysis. While the PEDOT morphology was discerned with round-shaped granular morphology where the average grain size was decreased with the electropolymerization potentials. The resistance of charge transfer of PEDOT/ZnO thin film was directly proportional to the electropolymerization potential while on the specific capacitance was inversely proportional. The composite exhibit both PEDOT and ZnO unique properties that can be used as a multi-functional material in various potential applications

Preparation of TiO2 compact layer by heat treatment of electrospun TiO2 composite for dye-sensitized solar cells

The power conversion efficiency (PCE) of the dye-sensitized solar cell was improved by using titanium dioxide (TiO2) compact layer prepared via heat treatment assisted electrospinning. Titanium tetraisopropoxide mixed with polyvinyl-alcohol was used as the electrospun solution. In this study, TiO2 photoanode with TiO2 compact layer was compared with TiO2 photoanode without TiO2 compact layer where the PCE was improved by 76.88%. Electrochemical impedance spectroscopy proved that the TiO2 compact layer can reduce the series resistance and improved the short circuit current density, resulting in a low recombination effect that leads to a higher PCE. The electron lifetime and charge collection efficiency of TiO2 nanoparticles with TiO2 compact layer displayed a higher value compared to TiO2 nanoparticles without TiO2 compact layer

Optimization of power conversion efficiency of polyvinyl-alcohol/titanium dioxide as light scattering layer in DSSC using response surface methodology/central composite design

This study focused on the optimization of polyvinyl-alcohol/titanium dioxide (PVA/TiO2) nanofibers as a light scattering layer in the dye-sensitized solar cell. The experiment was designed by response surface methodology with central composite design (RSM/CCD). Two parameters were studied i.e. electrospinning time and concentration of titanium tetraisopropoxide (TTIP). A quadratic model was used to determine the significance of each parameter studied towards the surface response which is power conversion efficiency (PCE). The statistical analysis showed that the electrospinning time and concentration of TTIP were significantly affected the PCE with the coefficient of variance (R2) of 0.9756. The RSM was able to predict the optimum condition of each parameter with less than 5% residual standard error

Light scattering effect of polyvinyl-alcohol/titanium dioxide nanofibers in the dye-sensitized solar cell

In the present work, polyvinyl-alcohol/titanium dioxide (PVA/TiO2) nanofbers are utilized as a light scattering layer (LSL) on top of the TiO2 nanoparticles photoanode. The TiO2 nanoparticles decorated PVA/TiO2 nanofbers display a power conversion efciency (PCE) of 4.06%, which is 33% higher than TiO2 nanoparticles without LSL, demonstrating the incorporation of PVA/TiO2 nanofbers as LSL reduces the radiation loss and increases the excitation of the electron that leads to high PCE. The incorporation of PVA/TiO2 nanofbers as LSL also increases the electron life time and charge collection efciency in comparison to the TiO2 nanoparticles without LSL

Development of titanium dioxide based compact layers and light scattering layers for enhanced dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs) are the third-generation solar cell that capable of converting solar energy into electrical energy. Titanium dioxide (TiO2) as a photoanode has faced a lot of drawbacks such as low dye loading capacity, a small range of light scattering, high recombination effect and low charge transport ability that subsequently reduces its power conversion efficiency (PCE). In this work, the enhancement of DSSC performance was studied by the modification of photoanode, specifically on the fabrication of a new compact layer (CL) and light scattering layers (LSLs). A dense, compact and homogenous TiO2 CL was optimized and prepared using response surface methodology by central composite design (RSM/CCD) and heat treatment assisted electrospinning, respectively. The TiO2 CL was successfully optimized with less than 5% residual standard error (RSE) and capable of enhancing the PCE up to 76.88% compared with the bare photoanode (1.73%). This is due to an improved electron lifetime (τn) and charge collection efficiency (ηc), resulting in a low recombination effect that leads to a higher PCE. Two LSLs were prepared in this study, namely polyvinyl alcohol (PVA/TiO2) nanofibers and TiO2 decorated by graphene quantum dot (TiO2-GQD). The PVA/TiO2 was prepared using electrospinning while TiO2-GQD was prepared via electrodeposition and drop-casting technique. Both PVA/TiO2 nanofibers and TiO2-GQD LSLs were successfully optimized using RSM/CCD with less than 5% RSE. Upon the addition of TiO2-GQD LSL onto the photoanode, the PCE increased up to 5.01% compared to the photoanode with PVA/TiO2 nanofibers LSL (4.06%) and bare photoanode (3.06%). This increment is due to the longer τn, higher ηc, higher dye loading capacity and higher light reflectance, demonstrating a good light scattering material. Furthermore, a fully flexible photoanode with TiO2-GQD LSL has successfully fabricated on indium doped tin oxide/polyethylene naphthalate (ITO/PEN) flexible substrate via electrodeposition and drop-casting technique. The fully flexible DSSC device consisting of photoanode with TiO2-GQD LSL showed an enhanced PCE of 5.18% compared to the bare photoanode (2.65%). The vast enhancement of PCE was due to the increase in the dye loading capacity (more dye can be adsorbed) and light scattering ability (more light can be scattered) upon the addition of TiO2-GQD LSL. In a nutshell, the introduction of CL and LSLs has successfully increased the DSSC performance

Study of poly(3,4-ethylenedioxythiophene) based counter electrodes for efficient dye-sensitized solar cell

In this work the enhancement of dye-sensitized solar cell (DSSC) performance was studied by developments of new counter electrode (CE) using a combination of three different materials namely poly(3,4-ethylenedioxythiophene) (PEDOT), carbon-based material (CBM; graphene oxide (GO), reduced graphene oxide (rGO), nanocrystalline cellulose (NCC) and multi-walled carbon nanotube (MWCNT)) and titanium dioxide (TiO2). The counter electrode was prepared by coating indium tin oxide (ITO) glass with TiO2 followed by deposition of PEDOT incorporated with different CBMs to produce novel CEs with high performance. Among the CEs PEDOT-NCC/TiO2 exhibited the highest PCE of 2.10 % compared to PEDOT-MWCNT/TiO2 (1.29 %), PEDOT-rGO/TiO2 (1.10 %) and PEDOT-GO (1.17 %). PEDOT-NCC/TiO2 also displayed a lower charge transfer resistance (Rct = 2.4 Ω) and higher cathodic peak current density (Icp = -2.60 mA.cm-2) compared to other CEs due to the synergistic effect of high conductivity of PEDOT, high surface area and high optical transparency of NCC and porous structure of TiO2 that provide large surface area. The impact of this study in photovoltaic technology is to produce an efficient and low cost CE that capable to substitute a typical CE in DSSC which is platinum that is expensive and rare metal. The future plan can be pursued by producing a flexible CE to increase its application in various fields

Fully flexible dye-sensitized solar cells photoanode modified with titanium dioxide-graphene quantum dot light scattering layer

Herein, we report the preparation of titanium dioxide-graphene quantum dot (TG) as a light scattering layer (LSL) using facile electrodeposition and drop-casting. A fully flexible DSSC device containing TG LSL was capable to generate efficiency of 5.18% which is 95% higher than the bare photoanode (2.65%). Upon the inclusion of TG LSL, the vast enhancement of efficiency was observed which attributed to the improvement in dye loading capacity and light scattering ability. The fully flexible DSSC also depicted higher charge collection efficiency compared to the bare photoanode, indicating enhanced light scattering ability

A Novel Poly(3,4-ethylenedioxythiophene)-graphene Oxide/Titanium Dioxide Composites Counter Electrode for Dye-Sensitized Solar Cell

PEDOT-based material counter electrodes (CEs) are recently given an enormous attention as new renewable energy sources due to their cost-effectiveness and accessibility, coupled with the simplicity of production. The existing dye-sensitized solar cells (DSSCs) are expensive because they are made using platinum-based glass electrode. In this work, a new CE, that is, poly(3,4-ethylenedioxythiophene)-graphene oxide/titanium dioxide (PEDOT-GO/TiO2) with a low charge transfer resistance (Rct=9.0 Ω), was fabricated. In addition, PEDOT-GO/TiO2 CE possesses a good electrocatalytic activity (ECA) toward the tri-iodide ions reduction and an improved efficiency of 1.166% was reached in DSSC

Facile fabrication of PVA nanofiber coated with PEDOT as a counter electrodes for dye-sensitized solar cell

Polyvinyl alcohol (PVA) nanofibers coated with poly(3,4-ethylenedioxythiophene) (PEDOT) as a counter electrode (CE) is a promising material to substitute platinum CE for dye-sensitized solar cell due to the high conductivity of PEDOT and high surface area to volume ratio of PVA. PVA nanofibers and PEDOT were prepared through facile techniques of electrospinning and electropolymerization, respectively. Field emission scanning electron microscopy revealed that PEDOT was distributed evenly on PVA nanofibers with porous cauliflower-like structure. PVA/PEDOT nanofibers CE had low charge transfer resistance (Rct) and possessed a good electrocatalytic activity with a low value of peak-to-peak separation (Epp = 0.34 V), thus an improved efficiency of 2.11% was obtained in comparison to platinum (1.14%), PEDOT (1.39%) and PVA nanofibers (0.017%)