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This study investigated the different thicknesses of TiO2 photoanode films and the effect of surface plasmon resonance (SPR) of Ag-TiO2 nanocomposites on the current-voltage (I–V) performance of dye-sensitized solar cells (DSSC). The TiO2 layer was deposited using the doctor blade technique and the thickness of the TiO2 films was controlled by using a different number of Scotch tape layers. The silver nanoparticles (AgNP) were synthesised using a chemical reduction method and the concentration of sodium citrate as a reducing agent was varied from 4 to 12 mM to study the effect of citrate ion on the size of the nanoparticles. Ag-TiO2 nanopowder was prepared by adding pure anatase TiO2 powder into AgNP colloidal solution. The mixture was left to dry for 24 h to obtain Ag-TiO2 powder for paste preparation. The three-layer Scotch tape, with thickness of 14.38 µm, achieved a high efficiency of 4.14%. This results showed that three layers was the optimal thickness to improve dye loading and to reduce the charge recombination rate. As for the Ag-TiO2 nanocomposites, 10 mM of AgNP, with a mean diameter of 65.23 nm and high efficiency of 6.92%, proved that SPR can enhance the absorption capability of dye and improve the photon-to-electron generation.

Dye-sensitized solar cells (DSSCs) with the capability of photon harvesting from both front and rear sides, consisting of newly developed NIR dye (SQ-140), iodine-based redox electrolyte, and transparent counter electrode with high bifaciality factor (BFF) and good cumulated photoconversion efficiency (PCE), are successfully fabricated and characterized. The use of transparent TiO2-based photoanode leads to improved BFF as compared to its opaque TiO2 counterparts: from 74% to 86% under similar experimental conditions and device parameters. The high molar extinction coefficient of the NIR dye SQ-140, needing a thinner TiO2 layer, was found to be advantageous to maintaining the high BFF even in thicker TiO2 films without serious compromise in the PCE. The lower efficiency of the bifacial DSSC under rear illumination was attributed to the hampered optical penetration as well as absorption of light by the intense colored iodine-based redox electrolyte.

In this study, a CQDs at different concentration is used to modify the TiO2 photoelectrode band gap which can improve light absorption of DSSC. The photoelectrode is immersed in different CQDs concentration at 2.5, 5.0, 7.5 and 10 mg/ml to study the effect on TiO2. It was found that photoelectrode with 7.5 mg/ml CQDs was successfully narrowing the TiO2 band gap and generated the highest photocurrent and power conversion efficiency at 17.06 mA/cm2 and 7.23% respectively, compared to pristine TiO2 (PT) at 10.94 mA/cm2 and 4.63% . The band gap narrowing mechanism for CQDs- TiO2 is obtained from the Tauc’s plot method using absorption spectra. The result shows a pristine TiO2 photoelectrode (PT) band gap is 3.38 eV, upon existing of CQDs, the band gap of all photoelectrodes with CQDs at 2.5, 5.0, 7.5 and 10 were reduced to 3.30 eV, 3.28 eV, 3.09 eV, and 3.29 eV respectively. PG 7.5 cell with lowest band gap at 3.09 eV generates effective electron transport from N719 dye to CQDs/ TiO2 layer compared to other photoelectrodes. The band gap narrowing effect is attributed from chemical bonds of Ti-O-C molecules between CQDs/TiO2. Thus, extra energy states are introduced between CQDs and TiO2. The location of these energy will present a quantum confinement effect which narrow the CQDs-TiO2 band gap which extend the light absorption to visible region.

Bifacial solar cells (BFSCs) are gaining popularity due to their compactness, space‐saving property, and higher photoconversion efficiency (PCE) than mono‐facial solar cells. Bifacial dye‐sensitized solar cells (BF‐DSSCs) are fabricated and characterized utilizing D‐205 as a dye‐sensitizer in combination with I‐/I3 ‐ and Co2+/Co3+ redox electrolytes. BF‐DSSCs using iodine‐based electrolytes demonstrate a cumulative PCE and bifaciality factor (BFF) of 13.05% and 85%, respectively. The hampered PCE under back‐side light illumination is attributed to the absorption of photons by the electrolyte itself. Contrary to this, BF‐DSSCs fabricated using cobalt‐complex‐based redox electrolyte exhibits an exceptionally high BFF of nearly 100% with a PCE of 4.77% and 4.75% under the front and rear light illumination, respectively. Although the open circuit voltage (Voc) of the BF‐DSSCs fabricated using cobalt electrolyte (with deeper redox potential) is slightly higher than that of BF‐DSSCs fabricated using iodine electrolyte, their cumulative PCE (9.52%) is much lower than that of iodine‐based device counterparts (13.05%). This decrease in PCE is attributed to the relatively fast charge recombination in the cobalt electrolyte‐based BF‐DSSCs.This article is protected by copyright. All rights reserved.