Synthesis And Properties Of The Polymers Based On Benzothiadiazole And Thiadiazolo[3,4-c]-Pyridine

The working principle,device structure,and the effects of structure on photovoltaic performance of bulk heterojunction(BHJ)polymer solar cells(PSCs)have been briefly introduced in this dissertation.Subsequently,the recent progress of some polymeric donor materials and acceptor materials in PSCs devices has been summarized.The photoelectric conversion efficiency(PCE)of a PSC device is determined by the absorption spectra,solubility,crystallinity,carrier mobility,energy level and aggregation of polymer donor material and acceptor material.Herein,the absorption spectra,energy levels and aggregation of the conjugated polymers have been tuned by introducing long alkylthiothiophene side chains,different fluorine(F)atoms,[1,2,5]Thiadiazolo[3,4-c]pyridine in order to obtain a high-performance polymers.The main research contents are listed below.1.5-((2-Hexyldecyl)thio)thiophene has been introduced as the side chains of benzo[1,2-b:4,5-b?]dithiophene(BDT)moieties in order to improving the solubility and depressing the highest occupied molecular orbital(HOMO)energy levels of the polymers.Moreover,three novel copolymers PST-BT,PST-1FBT and PST-2FBT,consisting of the BDT derivitive as the electron-donating moieties and benzothiadiazole(BT)derivitives with different fluorine atoms as the electron-accepte withdrawing moieties have been designed and synthesized.With increase of F atom number,the polymers show stronger intermolecular ?-? interaction and higher light-harvesting capacity.Moreover,three polymers exhibit low HOMO energy levels-5.45 eV because of the introducing of alkylthiothiophene side chains,so the BHJ PSCs devices present high open circuit voltage(Voc)over 0.90 V.The PSC devices based on PST-BT,PST-1FBT and PST-2FBT as electron donor materials and PC61 BM as electron acceptor materials were fabricated without any processing additive or posttreatment and exhibited PCE values of 1.31%,2.29% and 2.55%,respectively.2.Firstly,the [1,2,5]thiadiazolo[3,4-c]pyridine(PyT)derivative is designed and synthesized by introducing two 3-(2-octyldodecyl)-thiophene at both sides of PyT in order to improving the solubility and molecular weights of the polymers.Subsequently,The conjugated polymers PPy T-T,PPy T-(TT),PPyT-ff(T-T)are designed and synthesized by Stille coupling with the PyT derivative as electron-withdrawing moieties and thiophene,thieno[3,2-b]thiophene,and 3,3'-difluoro-2,2'-bithiophene as electron-donating moieties respectively.Compared with PPy T-T and PPy T-(TT),the polymer PPyT-ff(T-T)shows broader absorption spectrum,higher absorption coefficient,stronger interchain ?-? stacking because of the introducing of fluorine atoms,so the PSC device based on PPyT-ff(T-T)possesses higher short-circuit current density(Jsc)and PCE values.The PCE of the PSC devices based on PPy T-T/PC61 BM,PPy T-(TT)/PC61 BM and PPyT-ff(T-T)/PC61 BM are 1.57%,2.09% and 6.75%,respectively.