Design, Synthesis And Photovoltaic Performance Of Organic Functional Dyes

Dye-Sensitized Solar Cells(DSSCs)have the advantages of large total energy source,green pollution-free,low cost,simple structure and easy control,good flexibility,wide application range,safety and high efficiency,etc.DSSCs include photoanode,dye sensitizer,electrolyte and counter electrode.The dye sensitizer is the core part of the device.Phenothiazine has excellent electron donating properties,?-conjugated system and rigid structure.At the same time,the unique non-planar butterfly structure of phenothiazine can effectively inhibit the aggregation of dye molecules and inhibit the charge recombination behavior.It is an ideal dye electron donor structure.Therefore,in this paper,using phenothiazine as the electron donor,a series of novel structure and efficient phenothiazine organic dye sensitizers were synthesized and applied to DSSCs.The main research work is as follows:?The structure of N719 was further optimized,and two high-efficiency phenothiazine-ruthenium-based dye sensitizers JR1 and JR2 were designed and synthesized and applied to DSSCs.The IPCE response of JR1 is significantly improved,the photocurrent response range is expanded to 800 nm,and the overall response value is also higher.JR2 shows the widest and highest IPCE response curve.In the range of 410-600 nm,the IPCE value exceeds 70%,and at 530 nm,the IPCE value reaches 79%,so JR2 shows the highest J_SC(17.18 m A cm^-2).The optimization of the molecular structure not only improves the photon capture performance of the device,but also reduces the charge recombination behavior,prolongs the electron lifetime,and greatly improves the V_OC.Especially JR2,the introduction of the second long carbon chain not only increases the solubility of the dye,but also further inhibits the aggregation of the dye and reduces charge recombination.JR2 has high V_OC(841m V)and excellent conversion efficiency(9.12%),which exceeds N719(8.03%)by about 14%.?Two novel phenothiazine-zinc porphyrin dyes(JA4 and JA5)containing different anchoring groups were prepared.The hydrazide unit was developed as the anchor group,and the device based on JA5 containing the hydrazide anchor group also shows a high conversion efficiency of 5.49%.Carboxylic acid is the most common anchoring group,but it is easily dissociated from the TiO₂ surface,especially under alkaline conditions.Compared with carboxylic acid anchor groups,hydrazide anchor groups exhibit better water stability under various water conditions,including acidic,neutral and alkaline conditions.?Three D-A-?-A type phenothiazine stereo dyes JA0,JA6 and JA7 were prepared.The spectral response of JA6 reaches approximately 770 nm.The open circuit voltage values of JA0 and JA6 are both above 800 m V.In addition,we used carboxylic acid,cyanoacrylic acid and pyridine as anchoring groups to study the optical properties,electrochemical properties and photovoltaic properties of these dyes,and analyzed the influence of different anchoring groups on the performance of dyes.The results show that cyanoacrylic acid is the best anchoring group for this series of dyes.JA6 with cyanoacrylic acid as the anchoring group has a conversion efficiency of 7.34%.?Two organic dyes S3 and S4 were prepared and used as co-sensitizers to assemble solar cells with porphyrin dye JA3.After the two organic molecules are co-sensitized with the porphyrin dye JA3,the photon trapping ability of the device is significantly improved.At the same time,since the appropriate molecular volume structure of S3 and S4 can fill the adsorption gap between the porphyrin dye JA3,the charge recombination effect of the porphyrin dye is significantly reduced.The conversion efficiency of JA3 is 6.23%.After co-sensitization,the overall performance of the device has been significantly improved,and both J_SC and V_OChave been greatly improved.The conversion efficiency of JA3+S3 reaches 8.20%,V_OC is 821 m V,J_SC is15.46 m A cm^-2 and FF is 64.55%.?A-Zn-S series of self-assembly dyes were developed and applied to DSSCs.Two organic antenna chromophores S1 and S2 were prepared and coordinated with two receptors A1 and A2 through Zn to construct the A-Zn-S series of self-assembled dyes.The energy conversion efficiency of A2-Zn-S1 is 4.25%,which is higher than that of A1-Zn-S1(3.88%),A1-Zn-S2(3.21%)and A2-Zn-S2(3.52%),mainly due to the different coordination structures between the antenna chromome and the receptor.The devices based on A2-Zn-S1 show high V_OC(632 m V)and high J_SC(9.54 m A cm-2),due to the better spectral responsiveness of S1 and the better steric hindrance of A2,which effectively reduce charge recombination.In addition,infrared spectroscopy shows that these self-assembled dyes loaded on the surface of TiO₂through double carboxyl anchoring groups are also very beneficial to improve the performance of the dye.