Nanhai Sun

Thickness dependence of the MoO3 blocking layers on ZnO nanorod-inverted organic photovoltaic devices

Organic solar cells based on vertically aligned zinc oxide nanorod arrays (ZNR) in an inverted structure of indium tin oxide (ITO)/ZNR/poly(3-hexylthiophene): (6,6)-phenyl C61 butyric acid methyl ester(P3HT:PCBM)/MoO3/aluminum(Al) were studied. We found that the optimum MoO3 layer thickness condition of 20 nm, the MoO3 can effectively decrease the probability of bimolecular recombination either at the Al interface or within the active layer itself. For this optimum condition we get a power conversion efficiency of 2.15%, a short-circuit current density of 9.02 mA/cm2, an open-circuit voltage of 0.55V, and a fill factor of 0.44 under 100 mW/cm2 irradiation. Our investigations also show that the highly crystallized ZNR can create short and continuous pathways for electron transport and increase the contact area between the ZNR and the organic materials.

Deposition temperature effect of RF magnetron sputtered molybdenum oxide films on the power conversion efficiency of bulk-heterojunction solar cells

We have reported efficient bulk-heterojunction (regioregular poly (3-hexylthiophene) : (6,6)-phenyl C61 butyric acid methyl ester (P3HT : PCBM)) solar cells with MoO3 as a hole-selective layer deposited at different substrate temperatures from 100 °C to 400 °C by radio-frequency magnetron sputtering. The structure, morphology, optical and electrical properties of the MoO3 films deposited at different substrate temperatures are also investigated. MoO3 thin films deposited at 200 °C and below are amorphous in nature. However, the films deposited at 300 °C and 400 °C exhibit the presence of monoclinic Mo9O26 and orthorhombic MoO3, respectively. The electrical resistivity values of the MoO3 thin films are close to each other from 100 to 300 °C and decrease from 2.7 × 106 to 2.6 × 105 Ω cm with increasing substrate temperature from 300 to 400 °C. X-ray photoelectron spectroscopy core level analysis reveals the presence of Mo6+ oxidation state only in the films. We found that the optical band gap of MoO3 has reduced from 3.82 to 3.67 eV with decreasing substrate temperature from 400 to 100 °C. This decrease in band gap reduces the potential barrier between FTO and P3HT : PCBM, leading to an increase in the short circuit photocurrent density from 8.51 mA cm−2 to 9.50 mA cm−2 and an increase in efficiency of ~20.7%.

Efficient flexible organic solar cells with room temperature sputtered and highly conductive NiO as hole-transporting layer

We report efficient bulk-heterojunction [regioregular of poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61 butyric acid methyl ester(PCBM)] solar cells with a highly transparent and electrical conductive NiO film as hole-transporting layer (HTL). The highest power conversion efficiency (PCE) of 3.26% of FTO/NiO/P3HT : PCBM/Al solar cells on glass was achieved through NiO thin film sputtering temperature, film thickness optimization and it was found that NiO with 10 nm and sputtered at room temperature shows the best photovoltaic properties. Under the optimized condition, PCE of 2.5% on flexible substrate was achieved with highly electrical conductive and room temperature sputtered NiO as HTL.

The Application of Anode Material (ITAZO) and Hole Transportation Material (NiO) in Organic Solar Cell

The preparation and characteristics of AZO co-sputtered ITO (ITAZO) electrodes grown on glass substrates using a specially designed composite target for use in organic solar cells are described. It was found that both the electrical and optical properties of the ITAZO films were critically dependent on the Ar/O2 flow ratio and sputtering power. In addition, all ITAZO electrodes show amorphous structure regardless of the Ar/O2 flow ratio, due to the low substrate temperature. We obtained the ITAZO electrode with sheet resistance of 23 Ohm/square and average optical transmittance of 87.5 % in room temperature. The conversion power efficiency by using ITAZO electrode at optimized conditions is 3.2 %. In the mean time, the hole transportation material(NiO) for organic solar cell(OSC) has been investigated. And the conversion power efficiency at optimized conditions is 3.4%. Keywords—anode material, ITAZO, room temperature, NiO, OSC, power efficiency

Density Control of ZnO Nanorod Arrays by a Solution-Based Growth with a Large Temperature Change for Field Electron Emission Application

A simple, scalable, and cost-effective technique for controlling the growth density of ZnO nanorod arrays based on a large change in reactive temperature is demonstrated. The ZnO nanorods were synthesized using a low temperature (about 70-150 �� ), solution-based method. We divided the hydrothermally reaction into two temperature stages, a low temperature and a relative high temperature. The density-control technique utilizes a large change in reactive temperature to increase ununiformity among the neighborhood grown ZnO nanorods. The density-controlled arrays were investigated as potential field emission candidates. The field emission results revealed that an emitter density of 6 nanorods �� m I 2 generated a high field enhancement factor of 2452. This novel technique shows a possibility of applications in field emission display technology. Keywords—ZnO nanorod, hydrothermal method, field electron emission, density controll.