Influence of Dimethyl Sulfoxide as Processing Additive for Improving Efficiency of Polymer Solar Cells.

The effect of dimethyl sulfoxide (DMSO) doping concentration on the performance of polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT)∶(6,6)-phenyl C60 butyric acid methyl ester (PCBM) as the active layer was investigated. The results suggest that the doping of DMSO can improve short-circuit current density (Jsc) and fill factor (FF) of the PSCs. The cell with 3% DMSO exhibits enhanced Jsc (7.88 mA·cm-2), and FF (55.5%). The optimized power conversion efficiency (PCE) arrived to 2.54%, which is 17% higher than that of the cell without DMSO doping. The Fourier Transform infrared spectroscopy (FTIR) is used to demonstrate the effect of DMSO doping into P3HT : PCBM on chemical properties. The presence of FTIR suggests that the chemical properties of P3HT and PCBM have no changes. To investigate the causes of the PCE improvement after addition of DMSO, an enhanced light harvesting and charge carriers transport properties of electroluminescence devices were observed by UV-Visible spectra and J-V characteristics. The absorption peaks of P3HT : PCBM : DMSO thin film show a distinguished red shift and strong absorption compared to P3HT : PCBM thin films in the visible light range. It was considered that the increase of the Jsc was supported by this phenomenon of UV-Visible absorption. The charge carrier mobility change of the P3HT : DMSO films is studied by employing the donor-only devices. The increased performance should be attributed to the enhanced charge carrier mobility and widened absorption spectra of P3HT : PCBM through doping DMSO.

Direct synthesis of hydrophobic graphene-based nanosheets via chemical modification of exfoliated graphene oxide.

Hydrophobic graphene-based material at the nanoscale was prepared by treatment of exfoliated graphene oxide with organic isocyanates. The lipophilic modified graphene oxide (LMGO) can then be exfoliated into the functionalized graphene nanoplatelets that can form a stable dispersion in polar aprotic solvents. AFM image shows the thickness of LMGO is approximately 1 nm. Characterization of LMGO by elemental analysis suggested that the chemical treatment results in the functionalization of the carboxyl and hydroxyl groups in GO via formation of amides and carbamate esters, respectively. The degree of GO functionalization can be controlled via either the reactivity of the isocyanate or the reaction time. Then we investigated the thermal properties of the SPFGraphene by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the TGA curve shows a greater weight loss of approximately 20% occurred indicating removal of functional groups from the LMGO sheets and an obvious exothermic peak at 176 degrees can be observed from 150 to 250 degrees. We also compared the structure of graphene oxide with the structure of chemical treated graphene oxide by FT-IR spectroscopy. The morphology and microstructure of the LMGO nanosheets were also characterized by SEM and XRD. Graphene can be used to fabricate a wide range of simple electronic devices such as field-effect transistors, resonators, quantum dots and some other extensive industrial manufacture such as super capacitor, li ion battery, solar cells and even transparent electrodes in device applications.