Enhanced Performance of Flexible Dye-Sensitized Solar Cells: Electrodeposition of Mg(OH)₂ on a Nanocrystalline TiO₂ Electrode

Abstract

Nanocrystalline TiO2 photoanodes were prepared on a conductive indium–tin oxide coated polyethylene naphthalate (ITO-PEN) plastic substrate by the doctor-blade method to fabricate flexible dye-sensitized solar cells (DSCs). The surface of the photoanode was coated with Mg(OH)2 by electrodeposition and the deposition time was systematically varied (2, 4, 6, 8, and 10 min). Electrodeposited Mg(OH)2 was confirmed by IR and energy dispersive X-ray (EDX) analysis. The surface morphology was studied by scanning electron microscopy. The internal surface area of TiO2 was studied against the deposition time by taking into account the projected surface area of the photoelectrode and it shows that the internal surface area of the photoelectrode was reduced as the Mg(OH)2 deposition time increased. The performance of flexible DSCs on various deposition times of Mg(OH)2 was evaluated on the basis of their photocurrent density–voltage characteristics. Among the deposition times, 2 min showed the best performance in V oc on a treated flexible DSC, with resulting 847 mV and a photocurrent density of 7.13 mA/cm2, providing an overall light-to-electricity conversion efficiency of 4.01%. This photovoltage is among the highest attained for a flexible DSC to date. This notable increment in V oc at a thin layer of Mg(OH)2 was attributed to the suppression of recombination of photogenerated electrons via the exposed surface of ITO as well as TiO2 without influencing the internal surface area of the photoanode significantly.

Insights into mechanical compression and the enhancement in performance by Mg(OH)2 coating in flexible dye sensitized solar cells

“…Note that the performance of the cells observed in Fig. 5a are lower than in our previous work 14 due to the use of a LED light source. When solar simulated light is used similar results to 90 those reported were obtained (Fig.…”

Effect of Electrochemically Deposited MgO Coating on Printable Perovskite Solar Cell Performance

“…The images showed that the substrates are completely covered by electrodeposited flower-like Mg(OH) 2 spheres [13,27]. Figure 2c,d shows the cross-sectional images of devices C and D respectively.…”

“…In order to investigate the effect of MgO on the photovoltaic performance of printable PSCs During the electrodeposition of Mg(OH)2 in the devices B, C and D, the below electrochemical reactions could take place at the cathode surface [13], During the electrodeposition of Mg(OH) 2 in the devices B, C and D, the below electrochemical reactions could take place at the cathode surface [13],…”

“…This flocculated Mg(OH)2 in the solution can be hetero-coagulated on TiO2 and FTO electrostatically due to their opposite surface charges. (Isoelectric points of TiO2 ~ 6.2 FTO ~ 6 and Mg(OH)2 ~ 12) [13]. Once the electrodeposition is started, it is more likely that the low resistive exposed FTO surface (i.e., pinholes) and the TiO2 surface in the vicinity are coated with Mg(OH)2.…”

“…However, unevenness, surface defects and the presence of pin holes in this layer are often responsible for reducing the cell performance. Therefore, over the last years, many attempts have been made to enhance the overall cell performance of PSCs by retarding the back transfer of photo-generated electrons through the FTO/TiO 2 interface by surface modification of TiO 2 using insulating metal oxides [10][11][12] and hydroxides [13,14] or high band gap semiconductors [15,16] that form a blocking layer between the perovskite sensitizer and TiO 2 layer to block the back electron flow towards the HTM. For instance, TiO 2 modification with a monolayer of silane [17] and ZnO with 3-aminopropanioc acid self-assembled monolayer [18] have been found to enhance the device efficiency by retarding the back electron transfer processes of PSCs.…”