Characterizing the Role of Iodine Doping in Improving Photovoltaic Performance of Dye‐Sensitized Hierarchically Structured ZnO Solar Cells

Abstract

We report two novel types of hierarchically structured iodine-doped ZnO (I-ZnO)-based dye-sensitized solar cells (DSCs) using indoline D205 and the ruthenium complex N719 as sensitizers. It was found that iodine doping boosts the efficiencies of D205 I-ZnO and N719 I-ZnO DSCs with an enhancement of 20.3 and 17.9 %, respectively, compared to the undoped versions. Transient absorption spectra demonstrated that iodine doping impels an increase in the decay time of I-ZnO, favoring enhanced exciton life. Mott-Schottky analysis results indicated a negative shift of the flat-band potential (V(fb)) of ZnO, caused by iodine doping, and this shift correlated with the enhancement of the open circuit voltage (V(oc)). To reveal the effect of iodine doping on the effective separation of e(-)-h(+) pairs which is responsible for cell efficiency, direct visualization of light-induced changes in the surface potential between I-ZnO particles and dye molecules were traced by Kelvin probe force microscopy. We found that potential changes of iodine-doped ZnO films by irradiation were above one hundred millivolts and thus significantly greater. In order to correlate enhanced cell performance with iodine doping, electrochemical impedance spectroscopy, incident-photon-current efficiency, and cyclic voltammetry investigations on I-ZnO cells were carried out. The results revealed several favorable features of I-ZnO cells, that is, longer electron lifetime, lower charge-transfer resistance, stronger peak current, and extended visible light harvest, all of which serve to promote cell performance.

ZnO nanostructured materials for emerging solar cell applications

“…Dopants will ll the holes in the cell, thus increasing the recombination injected electron in the semiconductor. 34 Several materials such as iodine, 45 B, 46 Ag, 47 Li, 48 La, 49 Sr, 50 In, 51 and Nd 52 could be doped into the semiconductor lm of ZnO, according to some reports. Zhao et al used iodinedoped ZnO-based as a photoanode in dye-sensitized solar cells with indoline D205 and N719 as the sensitizers.…”

“…The efficiencies of the D205-I-ZnO based DSSC and N719-I-ZnO based DSSC were enhanced by 20.3% and 17.9%, respectively. 45 Mahmood and Park reported a cell fabricated with ZnO nanosheets doped with boron and using the N3 dye as a sensitizer, achieving a signicant enhancement in PCE (6.75%) in contrast to the undoped ZnO nanosheets (2.62%) and BZO lms only including nanosized crystallites (3%). 46 The work from Lanjewar et al revealed that upon doping with Ag, the band gap is sharply reduced and the resulting Ag:ZnO photoelectrode could absorb the visible light range to a great extent.…”

Enhanced Solar Photocatalytic Activity of Thermally Stable I:ZnO/Glass Beads for Reduction of Cr(VI) in Tannery Effluent

“…In continuation of previous studies (Zhao et al, 2013;Zheng et al, 2017), intrinsic ZnO and iodine-doped ZnO were grafted onto the glass beads through the SILAR method. Initially, glass beads were etched by dipping in 30% HNO 3 solution overnight at 30 °C, followed by washing with ethanol and deionized water.…”

Dual interfacial modifications of hierarchically structured iodine-doped ZnO photoanodes for high-efficiency dye-sensitized solar cells

“…ZnO CL pre-treatment and TiO 2 PL post-treatment. Herein it is worth noting that hierarchical IZnO aggregates instead of pure ZnO were chosen as the photoanode material mainly based on their proven multi-benefits: large surface area for dye adsorption, efficient scattering centers for enhanced light-harvesting efficiency, porous structure beneficial to good access of electrolyte to the dye, and additional light absorption in visible region as well [24,25]. More importantly, our previous work has demonstrated that the PCE of I-ZnO aggregates based DSC is obviously higher than that of ZnO aggregates based DSC.…”