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In this work, hole-conductor-free mixed organic cation perovskite solar cells based on carbon counter electrode were fabricated under air atmosphere with high humidity condition around 50%. The photovoltaic performance of the perovskite solar cells with mixed organic cation perovskite (FA)x(MA)1−xPbI3 by chemical modification the molar ratios x were demonstrated. The light harvesting abilities and crystal morphology could be controlled with x from 0 to 0.4 which resulted in a corresponding diversification of photoelectric properties in perovskite solar cells. Electrical impedance measurements were performed for investigating the electron transport issues in perovskite solar cells with various x. The optimized perovskite solar cells delivered a short-circuit photocurrent density of 21.63 mA/cm3, open-circuit voltage of 980 mV, fill factor of 0.45 and overall conversion efficiency of 9.53% as x = 0.3. The long-term stability of the optimized perovskite solar cells was exhibited and the overall conversion efficiency retained about 91% after 49 days in air with humidity around 50%. The hole-conductor-free perovskite solar cells based on carbon counter electrode have low-cost and bring a prosperous application foreground in the future photovoltaic community.

In this study, a uniform CdTe nanorods (NRs) arrays are grown on Ni substrates by a simple one-step electrochemical deposition method. The effects of deposition parameters such as the concentration of reactants and reaction time on the growth of CdTe NRs arrays are systematically investigated. Na2TeO3 and CdSO4 have a significantly different influence on the growth of CdTe NRs. With the increase of Na2TeO3 concentration, the diffraction intensity increases slightly at the peak (111) to promote axial growth. The diffraction intensity of (002) can increase with the concentration of CdSO4 increasing, which is conducive to lateral growth. The morphology of CdTe film varies from a thin layer to nanoparticles, and finally to NRs with the extension of time. Based on the characterization results, the possible growth mechanism of CdTe NRs arrays is proposed. The as-prepared CdTe NRs arrays are then embedded into CdS film, forming a novel three-dimensional (3D) heterojunction photovoltaic device. An extensive study of the effect of NRs length on device performance is presented. The results indicate that the device performance is highly dependent on the length of CdTe NRs, and a power conversion efficiency of 2.50% is obtained for optimal length of 1 μm. The better photovoltaic performance can be attributed to its efficient charge separation and direct pathways for carriers transport. What's more, this novel 3D nanostructured concept suggests great potential for other optoelectronic devices.

High performance perovskite light harvester layer on the TiO2 nanorods array is firstly prepared by an acetic acid vapor-assisted thermal annealing (HAc VATA) method. The crystallinity of CH3NH3PbI3 layer is improved through introducing HAc vapor. Furthermore, the pore filling fraction of TiO2 nanorods array is increased and the contact between TiO2 and CH3NH3PbI3 is enhanced. As a result, the HAc VATA devices exhibit an average PCE of 12.20%, which is 63.54% higher than that of the usual thermal annealing devices (7.46%).

The cadmium sulfide (CdS) film is deposited on the surface of cadmium telluride (CdTe) nanorods (NRs) by two different methods, successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) techniques. The influence of the deposition parameters on the properties of the films is investigated. Compared to SILAR, CBD is a simple and time saving technique, which can ensure full coverage and better growth of CdS on the surface of CdTe NRs. The photovoltaic characteristics of CdS sensitized CdTe films are also investigated. It is found that the CdTe/CBD-CdS thin film demonstrates excellent photoelectrical properties, which is ascribed to the large absorption coefficient of the material, indicating the potential applications in solar cells.

In this study, one step hydrogen treatment (OSHT) method is first used for disposing the amorphous TiO2 nanotubes with nanowires formed on top (designed as TTW) to directly prepare the TiO2 containing Ti5O9 (designed as H-TTW(Ti5O9)), and also the method simplify the steps, shorter reaction time and lower cost. Through the first-principle calculations, we can conclude that the Ti5O9 is a narrow-gap material, the valence bands and conduction bands move down relative to that of TiO2 and generate new energy levels between the bands. These phenomena can be attributed to the existence of oxygen vacancies (VO). The H-TTW(Ti5O9) exhibits a larger absorption intensity of light in range of 350–800 nm, and a better photoelectrochemical (PEC) performance at 1.4 mA/cm2. Thus, the experimental results indicated that the existence of Ti5O9 in TiO2 is a highly promising material in activating various visible light functionalities and improving photoelectrochemical (PEC) performance.

In this paper, we report CdS quantum dots (QDs) sensitized vertical growth two-dimensional titanium dioxide (TiO 2 ) nanosheets array films with oriented {001} facets for the first time. The TiO 2 nanosheets array films of thickness about 1.2 μm exposed 85% high-energy {001} facets were perpendicularly grown on transparent conductive fluorine-doped tin oxide (FTO) glass substrates by a simple one-pot hydrothermal method. The CdS QDs sensitized TiO 2 photoelectrode was carried out by successive ionic layer adsorption and reaction (SILAR). CdS QDs with a diameter less than 10 nm were uniformly anchored on the surface of the single-crystalline TiO 2 nanosheets with active {001} facets. Under AM 1.5 G illumination, the photoelectrode of CdS sensitized TiO2 nanosheets array is found with a photocurrent intensity of 3.24 mA/cm 2 at a potential of 0 V versus Ag/AgCl, which is much higher than that of the bare TiO 2 nanosheets array with 0.48 mA/cm 2 . The excellent photoelectrochemical properties of the novel photoanodes suggest that the TiO 2 nanosheets array films sensitized by CdS QDs have potential applications in solar cells.

a b s t r a c t We report the photoanodes consisting of CdS quantum-dots (QDs) sensitized actinomorphic hexagonal columnar ZnO (CdS QDs/AHC-ZnO) with ZnS passivation layer are applied for solar cells. Simple chemical solution synthesized AHC-ZnO films on transparent conducting glass substrates, and then, AHC-ZnO is functionalized with uniform CdS and ZnS QDs via successive ionic layer adsorption and reaction (SILAR) method. The as-prepared materials were characterized by XRD, SEM, TEM, UV-vis diffused reflectance absorption spectra and photovoltaic performances analysis. Photovoltaic performances results indicate the quantity of CdS QDs as well as the visible light absorption threshold can be effectively controlled by varying the coating cycles during the SILAR process, and the photocurrent density (Jsc) is greatly improved by increasing the amount of ZnS. By optimizing the AHC-ZnO with the amount of CdS and ZnS, the best efficiency of 1.81% was achieved for solar cell under AM 1.5 G illumination with Jsc = 7.44 mA/cm 2 , Voc = 0.57 V and FF = 43%.

In this study, the SnO2 spherical particles film was firstly grown directly on FTO substrates by using one step hydrothermal method, and CdS QDs were deposited on the surface of the SnO2 spherical particles to act a light absorber by using the successive ionic-layer adsorption and reaction (SILAR) method. The photovoltaic performances of the sensitized-type solar cells based on SnO2/CdS electrodes were investigated. A maximum 1.47 mA cm−2 short circuit current density and 0.22% conversion efficiency under one sun illumination has been achieved. These results demonstrate that the CdS QDs-sensitized SnO2 photoelectrode has a potential application in solar cells.

CdS quantum dots (QDs) coated TiO 2 nanorod arrays have been prepared via a two-step method. TiO 2 nanorod arrays were synthesized by a facile hydrothermal method, and CdS QDs were deposited on the nanorods by a sequential chemical bath deposition (S-CBD) technique. The surface morphology, structure, optical and photoelectrochemical behaviors of the core–shell nanorod array films are considered. A photocurrent of 2.5 mA/cm 2 , an open circuit photovoltage of 1.10 V, and a conversion efficiency of 1.91% were obtained under an illumination of 100 mW/cm 2 , when the CdS QDs deposited on TiO 2 nanorods film for about 7 cycles. The results demonstrate that the composite films are of excellence with respect to photovoltaic conversion.