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In this study, zinc aluminum layered double hydroxide (ZnAl-LDH) with a Zn/Al molar ratio 8/1 was synthesized via a facile urea method, and the mixed metal oxide (MMO) was prepared using the corresponding LDH as a precursor. In order to improve the performance of electron transport layer, we introduced graphene into ZnAl-MMO to prepare new nanocomposites, ZnAl-MMO/graphene, as promising photoanodes for dye-sensitized solar cell (DSSC). The bare ZnAl-MMO and formed ZnAl-MMO/graphene nanocomposites were characterized by X-ray diffraction (XRD), Raman spectra, scanning electron microscope (SEM) and UV–vis absorption spectrum, confirming the presence of graphene and the wurtzite type phase of ZnO. A series of DSSC were fabricated by the corresponding nanocomposites and a D205 as dye. The photovoltaic behavior of these cells based on different graphene concentration was further investigated by electrochemical method. It turned out that the introduced graphene facilitated the dye adsorption and light-scattering, which heightened the performance of DSSC. The DSSC based on ZnAl-MMO/0.2 wt.% graphene reached the best power conversion efficiency (PCE) of 0.51%, showing a rise of 25% approximately when compared with plain ZnAl-MMO.

A novelty method has been replenished for getting one kind of photoanode materials for dye-sensitized solar by an ingenious way. Using the ZnTi layered double hydroxide (LDH) as a precursor of photoanode materials, the ZnTi-LDH with different ratios were produced through urea method. Since the thermal treatment of LDH precursor at 500 ℃, the ZnTi mixed metal oxides (MMO) were easily obtained and then DSSC based on different ratios of ZnTi-MMO were fabricated with two kinds of dyes (C101 and Z907). The different ZnTi cationic ratios and diverse dyes make a big difference on the performance of DSSC. As the amount of Zn2+ increasing, the photocurrent and power conversion efficiency (PCE) of the cells first increase and then decrease. The optimal efficiency under C101 condition gets up to 1.57% at 9:1 cationic ratio of the ZnTi-LDH precursor. The C101 dye exhibits a more impressive performance than the Z907 where the DSSC is equipped with same MMO and other conditions.

The highly catalytic copper sulfide (CuS) thin films were designed and combined with the FTO substrates by the chemical bath deposition method and were used as counter electrodes (CEs) for the CdS/CdSe quantum dot-sensitized solar cells (QDSSCs) based on zinc titanium mixed metal oxides (MMOs) deriving from the layered double hydroxide precursor for the first time. Formation of CuS films was confirmed by X-ray diffraction and X-ray photon spectroscopy. The surface morphology of CuS films was observed by scanning electron microscopy (SEM). Systemic electrochemical test was used to investigate the catalytic performance of CuS films and the photovoltaic performance of QDSSCs. When the number of deposition cycles (30 min per cycle) was two, the CuS CEs of excellent performance were obtained. The CuS CEs exhibited higher performance for QDSSCs based on ZnTi MMOs than the conventional platinum (Pt) CEs. The best power conversion efficiency of CdS/CdSe QDSSCs using optimal CuS CEs reached 3.95%, which is more than twice higher than that of Pt CEs.

The TiO2 nanoparticles aggregation (TNA) was synthesized by a novel one-step hydrothermal method in this work. And for the first time we prepared a kind of jelly pastes of TNA used as photoanode for high-efficiency dye-sensitized solar cells (DSSCs). The prepared TNA provides larger specific surface area of 79.34 m2 g−1 compared with P25 nanoparticles (49.25 m2 g−1), which is beneficial of absorbing more dye molecules and contributes to high current densities. Moreover, the high scattering effect of TNA caused a strong absorption in the visible-light range increasing the number of excited charges and reducing the energy loss. The effect of various concentrations of TNA pastes for DSSCs was studied to explore the superiority of concentrated TNA pastes. The result shows the DSSC based on high-concentration pastes and double-layer film achieved the best power conversion efficiency (PCE) of 8.34 % corresponding the current density of 17.97 mA cm-2.

It has been reported that doping ZnO with metal ions can alter the band gap and immensely enhance electron transport. In this regard, to increase the efficiency of cost-effective dye-sensitized solar cells (DSSCs), we synthesized Cu-doped ZnO nanocomposites from layered double hydroxide (LDH) precursors via a facile method. LDH layers were homogeneously doped with Cu ions, and mixed metal oxides (MMOs) were obtained after annealing. The morphology and optical and electrochemical properties of the as-synthesized Cu-doped ZnO nanocomposites were systematically studied. The introduction of Cu ions increases the specific surface area of ZnO and increases light absorption in the visible region. The Cu-doped ZnO MMOs were used as the photoanode of DSSCs, and the effect of the amount of the Cu dopant on the performance of the solar cells was studied. At the optimal doping weight percentage of Cu (0.25 wt%), the solar cell based on Cu-doped ZnO MMO and D149 dye achieved the highest short-circuit current of 7.12 mA cm−2 and the highest power conversion efficiency of 1.50%.

The graphene oxide (GO)/zinc aluminum mixed metal oxide (ZnAl-MMO) was synthesized successfully and used as photoanode for the dye-sensitized solar cell (DSSC). ZnAl-MMO was prepared by a facile method using ZnAl-layered double hydroxide (LDH) as the precursor. After doping different amounts of graphene oxide in LDH, a series of GO/ZnAl-MMO nanocomposites were obtained and worked as photoanodes of the DSSC. The presence of graphene oxide was confirmed by X-ray diffraction (XRD), Raman and other characterizations, and the influence of graphene oxide on the properties of material and DSSC was studied in detail. The result presented that the introduction of graphene oxide improved the photovoltaic performance of the cell. As the amount of GO increases, the photocurrent of the cell first increases and then decreases. The performance of the cell doped 30 ml graphene oxide solution (1 mg/ml) was the best in this experiment and the excess graphene oxide led to the decrease of the efficiency. The best efficiency of DSSC with dye D205 based ZnAl-30 ml GO reached 0.55%, which was about 34% higher than that of plain ZnAl-MMO.

In this work, a series of zinc titanium mixed metal oxides obtained from the zinc titanium layered double hydroxides as precursor were prepared as the photoanode material of the CdS quantum dot-sensitized solar cells. CdS quantum dots were deposited on photoanodes by the successive ionic adsorption and reaction method. It was investigated that the effects of photoanode based on different Zn–Ti molar ratios on the photovoltaic performance of solar cells. The essential parameters of samples were investigated by UV–vis absorption spectrum, incident photon-to-current conversion efficiency, photoelectric conversion efficiency and electrochemical impendence spectrum. The varying Zn–Ti ratios influence adsorption properties and charge mobility. As a result, the cells based on Zn–Ti MMOs achieved an optimum power conversion efficiency of 2.71% when the Zn–Ti ratio is 7:1.

The surface passivation strategy is one of the effective ways to improve the power conversion efficiency (PCE) of quantum dots-sensitized solar cells (QDSSCs). In this work, a novel ZnS/SiO2 coating serves as the passivation layers for the CdS/CdSe co-sensitized solar cells based on zinc titanium mixed metal oxides (MMOs) obtained from layered double hydroxides (LDHs) precursor. The incorporation of passivation layers effectively improved the performance of the corresponding CdS/CdSe quantum dots co-sensitized solar cells and the best PCE of 4.91% has been achieved, which represents an over 55% improvement than that of devices without passivation. The effects of ZnS/SiO2 double passivation layers were systematically investigated, especially by 2D time-resolved fluorescence imaging and electrochemical impedance spectroscopy technique. It was revealed that the existence of ZnS/SiO2 outer layers caused the suppression of charge recombination, higher electrons collection efficiency, and superior surface quality.

New photoanode based on zinc titanium mixed metal oxide (MMO) was successfully prepared using the layered double hydroxide precursor. The successive ionic layer adsorption and reaction method and chemical bath deposition method were used to fabricate CdS/CdSe co-sensitized quantum dot sensitized solar cells (QDSSCs). When the reaction cycle of CdS quantum dot is nine, the highest power conversion efficiency of 2.85% has achieved, with the lowest recombination rate and the biggest current density. This work demonstrated that 9 cycles of sensitization of CdS QD was the best for the CdS/CdSe QDs co-sensitized solar cells based on ZnTi MMO photoanode.