Enhanced Power Conversion Efficiency of Dye-Sensitized Solar Cells by Band Edge Shift of TiO2 Photoanode

Abstract

By simple soaking titanium dioxide (TiO2) films in an aqueous Na2S solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage (Voc) and the fill factor (FF) was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control cell without any modification. The UV–visible absorbance spectra, UPS valence band spectra, and dark current measurements revealed that the Na2S modification led to the formation of anions on the TiO2 surface, and thereby shifted the conduction band edge of TiO2 in the negative (upward) direction, inducing an increase of 29 mV in the Voc. It was also found that the increased FF value in the surface-treated device was attributed to an elevation in the shunt resistance.

Elucidating the Factors Affecting Hydrogen Production Activity Using a CdS/TiO2 Type-II Composite Photocatalyst

“…Therefore, in solutions containing amines (e.g., TEOA) and alcohols (e.g., MeOH), which adsorb somewhat more strongly to TiO 2 than water, , higher hydrogen overvoltages are observed along with higher total numbers of trapped electrons . On the other hand, in the case of a sulfide reducing agent, which adsorbs relatively weakly, a lower hydrogen overvoltage and fewer trapped electrons are observed (Figure c).…”

Study of Optical and Electrochemical Properties of Solvent-Dependent Natural Dye Extracted from <i>Rivina humilis</i> L

“…In addition, the HOMO level of each dye was -4.89 eV, -5.06 eV, and -5.16 eV for extracted dyes with aquades, acetone, and ethanol solvents, respectively. It is evident that the LUMO energy levels of the extracted dyes exhibit a significant positive energy difference compared to the TiO 2 CB (-5.11 eV) at a vacuum level (Sung et al, 2020). The HOMO levels of dyes indicate negative values compared to the electrolyte's energy level (-4.85 eV) (Güzel et al, 2018;Sung et al, 2020).…”

“…It is evident that the LUMO energy levels of the extracted dyes exhibit a significant positive energy difference compared to the TiO 2 CB (-5.11 eV) at a vacuum level (Sung et al, 2020). The HOMO levels of dyes indicate negative values compared to the electrolyte's energy level (-4.85 eV) (Güzel et al, 2018;Sung et al, 2020). This property enables the effective regeneration of oxidized dyes via electrolytes.…”

Enhancement in Photovoltaic Performance of Solar Cells by Electrostatic Adsorption of Dyes on ZnO Nanorods

“…The Φ coll value can be estimated from the lifetime of the electrons injected from the photoexcited dyes, i.e., a longer electron lifetime can enhance the Φ coll value [41]. As presented in Figure 7, we could calculate the electron lifetime (τ) of DSCs with the pristine ZnO/FTO and Ag + (20)-ZnO/FTO electrodes using OCVD measurement results Figure 7a and Equation (1); where k is the Boltzmann constant, T is the temperature, e is the electron charge, and dV oc /dt is the derivative of the V oc transient [42,43].…”