Preparation Of Ag/C Composites And Their Applications In Acceptor Materials Of Polymer Solar Cells

Up to now, although silicon-based solar cells and thin film solar cells havebeen commercialized, high material and manufacturing costs limit their wideacceptance. Polymer solar cells are promising green energy systems that possessmany advantages, such as light weight, low cost and mechanical flexibility. Lowdevice efficiency is a major factor which restricts the commercialization ofpolymer solar cells. One of the ways to improve device performance is theimprovement of the device structure, and the other is the selection of activelayer materials. Carbon nanosphere as a kind of fullerene-like material, hassimple preparation process, low cost, excellent physical and chemical properties,and is expected to become a potential acceptor material in polymer solar cells.Our group has used carbon nanosphere as acceptor material in preliminaryexploration, but the efficiency was very low. In this work, noble metal wasintroduced into carbon spheres to improve device performance.In this paper, Ag/C composites were prepared with one-step hydrothermalmethod using silver nitrate and glucose as raw materials. The effects of rawmaterials concentration and reaction time were investigated. Then, two typical composite materials were selected and their electrochemical properties wereanalyzed as acceptor of P3HT-based (poly (3-hexylthiophene)-based) polymersolar cells. The P3HT/(Ag/C) composite films were obtained by spin-coatingmethod. The influence of spin speed and blending mass ratio on opticalperformance of the composite films was analyzed by ultraviolet-visiblespectrophotometry and fluorescent spectrometry. Finally, the composite filmsprepared under optimal parameters were used as active layer and theirphotovoltaic properties were explored. The results are shown below:1. The composite materials of sandwich-like structure and core-shellstructure were synthesized under mild hydrothermal conditions at190℃and200℃, respectively. Revealed by cyclic voltammetry, the highest occupiedmolecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)of the sandwich-like materials are-5.55and-4.4eV, respectively. The HOMOand LUMO of the core-shell materials are-5.69and-4.68eV, respectively. Theyare all suitable for use as acceptor materials in polymer solar cells.2. When P3HT:Ag-C-Ag ratio was2:1and1:1under the spin-coatingspeed of1000rpm, the fluorescence quenching of resultant composite filmswere obvious; When the ratio of P3HT and Ag-C-Ag NPs was1:1under thespin-coating speed of1500rpm or when blending mass ratio was2:1, thespin-coating speed was1000rpm, the quenching phenomenon of the resultantcomposite film was the most evident. The observed quenching phenomenonmeans the separation rates of excitons is high, which is conducive to efficient charge transport. When P3HT:Ag-C-Ag ratio was2:1under the spin-coatingspeed of1000rpm, the enhancement of light absorption peak was morepronounced;3. The P3HT and Ag@C composite films possess apparent quenchingphenomena and enhanced absorption in300-800nm range, especially for thecomposite film prepared under the spin-coating speed of1000rpm, with theratio of2:1(P3HT:Ag@C, w:w);4. Compared with pure carbon-nanosphere based device, the efficiency ofP3HT/Ag-C-Ag based device increased by414%, and that of P3HT/Ag@Cbased device increased by386%;...