Semiconducting Divalent Metal Oxides as Blocking Layer Material for SnO₂-Based Dye-Sensitized Solar Cells

Abstract

This study is to demonstrate that semiconducting materials can be used as the blocking layer material for the electrode of dye-sensitized solar cells (DSSCs) as well as insulating materials studied previously. We modified SnO2 nanoparticles with various semiconductor divalent metal oxides (CdO, ZnO, NiO, CuO, and PbO) and fabricated DSSCs with the modified SnO2 nanoparticles. The modifier metal oxides exist as very small nanoparticles, well dispersed on the surfaces of SnO2 nanoparticles. Except for the case of PbO, all of the modifier materials improve the solar cell efficiency. The detailed mechanisms have been investigated. The basic properties of the modifiers increase the amount of dye adsorbed, increasing the current, and raise the flat-band potentials through deprotonation of the surface to increase the potentials. The coating materials block the recombination reactions between the electrons in the conduction band and the red–ox species in the electrolyte. Therefore, although the narrow band gaps and the d–d transitions of the coating materials may reduce the amount of photons to reach the sensitizer, such negative effects are reduced by the quantum size effects of the modifier metal oxides and are more than offset by the positive effects mentioned above. The case of PbO as the coating material appears to suffer from the high resistance arising from the highly anisotropic crystal structures of PbO. On the basis of the various observations depending on the nature of the modifier materials, a few suggestions are made in selecting good modifier materials.

NiO-decorated mesoporous TiO2 flowers for an improved photovoltaic dye sensitized solar cell

“…4 (a-c The open-circuit voltage decay (OCVD) technology has been widely used to study the electron lifetime in a photochemical cell and some other useful information of the recombination process between the injected electrons in TiO 2 and the electrolyte under the open-circuit and dark state. [35][36][37] The electron lifetime (recombination response time, t n ) for these devices under opencircuit conditions is calculated from the decay curve of the photovoltage by the following eqn (1):…”

Nanostructured copper oxide semiconductors: a perspective on materials, synthesis methods and applications

“…CuO is commonly used as a blocking layer that prevents recombination reactions by forming a potential barrier between the anode and the electrolyte which enhances the PCE of the device. [240][241][242][243] Yet in other experiments, the use of Cu 2 O at the photoanode of a DSSC was found to decrease the overall PCE. 244 This is due to the dissociation of Cu x O in liquid-based electrolytes, inducing numerous extrinsic defects that increase carrier recombination, resulting in photovoltaic performance degradation.…”

Enhanced Reactant Activation and Transformation for Efficient Photocatalytic Acetone Degradation on SnO2 via Hf Doping

“…Tin dioxide (SnO 2 ), as one of the representative of photocatalysts, is a n-type semiconductor accompanied by a wide bandgap of 3.48 eV, [18,19] and is applied generally in gas sensors, [20] storage of solar energy, [21] lithium batteries, [22] as well as photocatalytic decomposition of VOCs [23,24] since its outstanding stability, rather positive valence band (VB) and the electron transport ability. Nevertheless, the pristine SnO 2 exhibits a relatively quick recombination of electron and hole pairs and inadequate oxidation ability which could lead to restricted photocatalytic activity.…”