| Solar energy is a renewable and clean source, and it is one key direction for solving world energy needs. In the past decade, reducing the fabrication cost of silicon devices, great efforts have been made to improve the power conversion efficiency (PCE) of polymer solar cells (PSCs) by designing and synthesizing new conjugated polymers, because the PCE of most polymer-based devices are less than 5%. In this study, a series of tri-functionalized perylene bisimide (PBI) derivatives and novel conjugated polymers were synthesized for organic photovoltaic application.1?Three new asymmetrical 1-alkoxy-6,7-diphenoxy-substituted PBI 5, 6,7 with undecenyloxy or propyloxy group at bay position were designed and synthesized from the corresponding 1,6,7-triphenoxy-PBI 3, 4 by SNAr2 reaction. They were added in PSC active layer as additives. Interestingly, only tri-phenoxy-PBI showed reactivity by this methodology, but tetra-phenoxy-PBI 8 didn't. Ether exchange method was founded to be a simple way to introduce only one functional group, such as C=C, onto the perylene bay at 1-position in yield of 55-74%, with low reaction temperature(66 ?) and short reaction time (2 h). The structures of these compounds were confirmed by 1H, 13C, and DEPT135 NMR. The photophysical and electrochemical properties of these perylene derivatives were studied by UV-vis, fluorescence spectra and cyclic voltammograms.2?Six PBIs were added into PSC active layer, which was consisting of P3HT/PC61BM. The best cell was obtained from 1-undecenyloxy-6,7-diphenoxy-substituted PBI 5, showed an enhanced JSC of 9.85 mA cm-2 and a PCE of 3.57%, which were an increase of 7.8% and 5.6%compared to the control device, respectively. The effective sunlight harvesting capability of PBI additives results in an improved Jsc, EQE and efficiency.We also found that asymmetrical long alkyl-substituted PBI 5, 6 were better than tri-phenoxy PBI 3, 4, short alkyl-substituted PBI 7 and tetra-phenoxy-substituted PBI 8 in Jsc aspect.3?Stille and Suzuki methods were used to synthesized two ?A?benzothiadiazole (BT) and octyloxyl-benzothiadiazole (OBT) accepter units A1 and A2. Novel nAnAn acceptor units A3, OBT-DT-3, DT-BT-3 were synthesized by asymmetrical and symmetrical Stille routes. The structures of new pentmers were confirmed by 1H ,13C NMR. The optical energy gaps and energy levels of these eight monomers or precursors were calculated from UV-vis spectra and cyclic voltammograms.4?Two different molecular weight D?A?A medium bandgap copolymers X2-717 (Mw=31 kDa) and X2-526 (Mw=20 kDa) were obtained by Suzuki cross-coupling polymerization of OBT units with carbazole. D?A conjugated copolymer X1 (Mw=87 kDa) was also prepared from Suzuki coupling reaction with high molecular weight and yield. The chemical structures and molecular weights of them were determined by 'H NMR and GPC. The thermal properties of three polymers were investigated by TGA and DSC. The optical and electrochemical properties of D?A and D?A?A polymers were investigated by UV-vis and cyclic voltammetry. Energy levels were calculated.5?We fabricated the device with the structure of ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al, where D?A?A and D?A polymers X1 and X2-717, X2-526 were used as the electron donors. After optimization and post solvent annealing, D?A?A polymer X2-717 device showed best PCE of 4.74% with high Voc = 0.99 V, enhanced Jsc = 9.70 mA Cm-2. PCE and Jsc are 17% and 26% higher than that of D?A polymer X1, respectively. |
PDF Full Text Request