Haiteng Wang

Influence of Polymer/Fullerene-Graphene Structure on Organic Polymer Solar Devices

The dependence of device performance has been measured for solar cells using blends containing the conjugated polymer, poly (3-hexylthiophene) (P3HT) with two different functionalized electron acceptor commercially available [6,6]-phenyl C-60 butyric acid methyl ester (PC60BM) and graphene derivative to increase the carrier mobility which was produced in this laboratory. Performance was characterized by short-circuit current–open circuit voltage output of the devices. The interrelationships between UV-Vis absorption, fill factor and energy conversion efficiency (ECE) have been simulated. It is observed that the ECE of the device with low concentration of solution-processable functionalized graphene (SPFGraphene) has been increased significantly compared with the device without SPFGraphene. The improved performance is attributed to the presence of semiconducting graphene which provides charge-transport pathways for carriers to be extracted and hence boosts carrier mobility in organic photovoltaic (OPVs) devices. However, when the concentration of SPFGraphenes increased up to certain degree, the performance of the device decreased. By analysis on the intensity dependent photocurrent, the decreased performance is attributed to the PC60BM-graphene which causes bimolecular recombination of free carriers. In addition, the active layer films were also investigated by XRD and SEM in order to understand the crystallite and morphology of the hybrid films.

Graphene as the electrode material in supercapacitors

Supercapacitors, a new energy storage element based on electrochemical double layer capacitance, store energy by ion adsorption, have recently attracted increasing interest with the sharp development of nanostructure materials. Supercapacitors store and release energy by nanoscopic charge separation at the interface between an electrode and an electrolyte, and the energy restored in it is inversely proportional to the thickness of the double layer. Due to its high power density, long cycle life, low weight, flexible packaging and a wide thermal operating range compared to other conventional energy storage devices, supercapacitor can be used as a potential energy device bridging the gap between chemical power and common electrostatic capacitance. However, a distinct defect for supercapacitor is the energy density lower than rechargeable batteries. Electrode material is the key to improve the performance of supercapacitor, so most of researches current is around searching electrode materials with higher specific capacitance. Fortunately, graphene as a single atomic of graphite was found to be suitable for electrode materials in supercapacitors owing to its super conductivity and high specific area. In this paper, we report a study on graphene as the electrode material in supercapacitor.

Improving photovoltaic properties by incorporating graphene into P30T/PCBM photovoltaic devices

Summary form only given. We report the optoelectronic properties occurring in solution-processable functionalized graphene(SPFGraphene)-PCBM/poly(3-octylthiophene)(P3OT) composites. The structural configuration of devices is ITO/PEDOT:PSS/P3OT:PCBM-SPFGraphene/LiF/Al. The best results were obtained with a P3OT/PCBM (1:1) mixture with 8wt% of SPFGraphene is open-circuit voltage (Voc) of 0.65V, a short-circuit current density (Jsc) of 4.2mA/cm2 and a FF of 0.35 which led to a power conversion efficiency of 0.95% at illumination at 100mW/cm2 AM 1.5. In the P3OT:PCBM-SPFGraphene composite, the SPFGraphene acted as exciton dissociation sites and provided the transport pathway of LUMO-graphene-Al. Doping of SPFGraphene into P3OT resulted in appropriate energetic distance between HOMO and LUMO of the donor/acceptor for a high open circuit voltage and provided higher exciton dissociation volume mobility of carrier transport for a large short-circuit current density.