Electrodeposition of nanoporous ZnO on Al-doped ZnO leading to a highly organized structure for integration in Dye Sensitized Solar Cells

Abstract

In the present study, we propose an improvement of the anode configuration in Zinc Oxide based Dye Sensitized Solar Cells (DSSC). Instead of the classical configuration, which is composed by two different metal oxides: one transparent conducting oxide (TCO) for the substrate and one nanostructured metal oxide for supporting the dye, the new approach is to use ZnO as unique material. Thus, nanoporous zinc oxide films have been electrodeposited on a sputtered Al doped ZnO layers with varying thicknesses up to 6 µm. The evolution of the porosity of the structure has been studied by scanning electron microscope (SEM) and electrochemical impedance spectroscopy and compared with standard nanoporous ZnO grown on fluorine doped tin oxide (SnO2:F noted FTO). This results firstly in the modification of the nanoporous structure morphology and secondly a better adhesion between the nanoporous layer and the substrate. Organization in the nanoporous material is enhanced with regular pores arrays and perpendicular to the substrate. Dye sensitized solar cells based on this simplified architecture present efficiencies up to 4.2% and 4.5% with N719 and D149 respectively as sensitizers. Higher fill factor and Voc are found in comparison with the one obtained for deposition on the classical transparent conducting oxide (FTO), which denote improved electrical transfer properties.

The effect of dopant concentration on properties of transparent conducting Al-doped ZnO thin films for efficient Cu2ZnSnS4 thin-film solar cells prepared by electrodeposition method

“…All samples exhibited an intensive hexagonal ZnO (002) plane, indicating a c-axis preferred orientation, which was significantly enhanced because of Al incorporation. The spectra showed very sharp diffraction peaks that indicate high crystallinity (Haller et al 2011).…”

Zinc oxide films grown by galvanic deposition from 99% metals basis zinc nitrate electrolyte

“…Additionally, the low electron mobility values reported in the literature (see Table 1) even for apparently well crystallised compact lms indicate that electrical charge transport in the lateral direction is limited. However, the successful application of similar lms in various types of photovoltaic solar cells, 9,23,24 despite the poor electrical properties measured using methods probing the charge transport parallel to the substrate, is evidence that they have appreciable carrier mobility in the direction perpendicular to the substrate. One explanation could be that for extrinsically doped ECD grown lms ZnO lms with grains oriented perpendicular to the substrate, the intra-grain electron mobility is high enough such that the lms have a higher conductivity in the transverse direction (perpendicular to the substrate) than in the lateral direction (parallel to the substrate).…”

“…18 As a result, electrochemically deposited ZnO, in its diverse shapes, has found application in different types of photovoltaic devices for example, thin lm silicon solar cells, 19 all oxide solar cells, 20 CuInGaS(Se), 9,21,22 organic solar cells 23 and dye sensitized solar cells. 24 However, the two main drawbacks of electrochemical depositions are the requirement for a conductive substrate and high sensitivity to the purity of the precursors.…”

Synthesis and Characterization of Electrodeposited Zinc Oxide Nanostructures for Dye Sensitized Solar Cells - A Review

“…ZnO films have been prepared using electrodeposition method onto fluorine doped SnO 2 glass by Haller et al, 29 . The obtain films indicate tilted pores of various orientations in scanning electron microscopy studies.…”