Papers by Author: Nan Hai Sun

Abstract: The development of CdTe/CdS solar cells on flexible substrates is reviewed in this article. Photovoltaic structures on lightweight and flexible substrates have several advantages over the heavy glass based structures in both terrestrial and space applications. The cells mounted on flexible foil are not fragile, the requirements of the supporting structures are minimum and they can be wrapped onto any suitably oriented or curved structures. The specific power of the solar cells is an important factor in space applications and hence development of photovoltaic devices on light weight substrates is interesting. CdTe is one of the leading candidates for photovoltaic applications due to its optimum band gap for the efficient photo-conversion and robustness for industrial production with a variety of film preparation methods. Flexible solar cells with conversion efficiencies exceeding 11% have been developed on polyimide foils. The development of CdTe devices on metallic substrates is impeded due to the lack of a proper ohmic contact between CdTe and the substrate. The polymer substrate has the advantage that the devices can be prepared in both “superstrate” and “substrate” configurations.

Abstract: Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester(PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs).With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope,we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM.

Abstract: A thin Ag layer embedded between layers of zinc tin oxide (ZTO) are compared to cells using an indium tin oxide electrode was investigated for inverted organic bulk heterojunction solar cells employing a multilayer electrode. ZTO/Ag/ ZTO (ZAZ) electrode is the preparation at room temperature, a high transparency in the visible part of the spectrum, and a very low sheet resistance comparable to treated ITO without the need for any thermal post deposition treatment as it is necessary for ITO. The In-free ZAZ electrodes exhibit a favorable work function of 4.3 eV and are shown to allow for excellent electron extraction even without a further interlayer. This renders ZAZ a perfectly suited bottom electrode for inverted organic solar cells with simplified cell architecture.

Abstract: A new buffering layer(nickle oxide thin film) of organic solar cells was presented. The device strcture is Anode/NiO/P3HT[regioregular of poly(3-hexylthiophene)]: PCBM[(6,6)-phenyl C61 butyric acid methyl ester] /Al. Nickle Oxide(NiO) thin film is a good alternative of hole tansporting layer. We investigates the film from physical and electrical aspects, such as morphology, deposition temperature, thickness etc. The best power conversion efficiency of device we got with NiO buffering layer is 2.49%, which is hundred times of ones without NiO buffering layer.We find that the optimum fabrication conditions are: room temperature deposition, 10nm of thickness, and 30% oxygen proportion.

Abstract: An efficient flexible organic solar cell was presented. The highest power conversion efficiency (PCE) of 3.2% and 2.5% were achieved on glass substrate and flexible substrate individually. The device photovoltaic properties were discussed in terms of the band diagrams and series resistance of the devices. Also the properties of nickle oxide thin film on different conditions were investigated too. Room temperarure sputtered and highly conductive nickle oxide (NiO) thin film as hole transporting layer in the cells. The strcture of this kind of devices is PET/ITO/NiO/P3HT: PCBM [regioregular of poly (3-hexylthiophene):(6,6)-phenyl C61 butyric acid methyl ester] /Al. On the study of characteristics of Nickle oxide thin film, such as sputtering temperature, thickness, and oxygen proportion, we found that NiO with 10 nm and sputtered at room temperature shows the best photovoltaic properties.

Abstract: The preparation and characteristics of ZnO(Zinc oxide) co-sputtered TaO (Ta oxide) electrodes(ZTO) 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 ZTO films were critically dependent on the Ar/O2 flow ratio and sputtering power. In addition, all ZTO electrodes show amorphous structure regardless of the Ar/O2 flow ratio, due to the low substrate temperature. We obtained the ZTO electrode with sheet resistance of 30 Ohm/square and average optical transmittance of 80% in room temperature. The conversion power efficiency by using ZTO electrode at optimized conditions is 2.6 %.

Abstract: Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester(PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs).With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope,we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM.

Abstract: This paper presents an efficient flexible organic solar cell with room temperarure sputtered and highly conductive nickle oxide (NiO) thin film as hole transporting layer. The strcture of this kind of devices is PET/ITO/NiO/P3HT: PCBM [regioregular of poly (3-hexylthiophene):(6,6)-phenyl C61 butyric acid methyl ester] /Al. On the study of characteristics of Nickle oxide thin film, such as sputtering temperature, thickness, and oxygen proportion, we found that NiO with 10 nm and sputtered at room temperature shows the best photovoltaic properties. The highest power conversion efficiency (PCE) of 3.26% and 2.5% were achieved on glass substrate and flexible substrate individually. The device photovoltaic properties were discussed in terms of the band diagrams and series resistance of the devices. Also the properties of nickle oxide thin film on different conditions were investigated too.

Abstract: The preparation and characteristics of ZnO(Zinc oxide) co-sputtered TaO (Ta oxide) electrodes(ZTO) 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 ZTO films were critically dependent on the Ar/O2 flow ratio and sputtering power. In addition, all ZTO electrodes show amorphous structure regardless of the Ar/O2 flow ratio, due to the low substrate temperature. We obtained the ZTO electrode with sheet resistance of 30 Ohm/square and average optical transmittance of 80% in room temperature. The conversion power efficiency by using ZTO electrode at optimized conditions is 2.6 %.

Abstract: This paper presents a new buffering layer(nickle oxide thin film) of organic solar cells. Nickle Oxide(NiO) thin film is a good alternative of hole tansporting layer. We investigates the film from physical and electrical aspects, such as morphology, deposition temperature, thickness etc. We find that the optimum fabrication conditions are: room temperature deposition, 10nm of thickness, and 30% oxygen proportion. The device strcture is Anode/NiO/P3HT[regioregular of poly(3-hexylthiophene)]: PCBM[(6,6)-phenyl C61 butyric acid methyl ester] /Al. And the best power conversion efficiency of device we got with NiO buffering layer is 2.49%, which is hundred times of ones without NiO buffering layer.