Research Of Novel Acceptors And Interfacial Modification For Polymer Solar Cells

Polymer solar cells?PSCs?are a hot research in the field of organic optoelectronics and photovoltaics,which have been developed for more than thirty years gradually moving towards maturity.All kinds of new materials,new cell structures and preparation processes have been developed;the power conversion efficiency?PCE?of PSCs has exceeded 10%.It should continue to study the high performances of solar cell materials in order to realize the low-cost large-scale commercial applications of PSCs as soon as possible,partly solving the energy crisis for the benefit of society.This thesis is main focus on the novel acceptor materials and cathode interfacial materials of PSCs.The study of acceptor materials mainly aims at the chemical modification of fullerenes(C₆₀),and the influence of different side chain functional groups on the photovoltaic properties was discussed.The different types of organic small-molecule materials as cathode interfacial materials by wet process were designed and synthesized,including conjugated molecules and non-conjugated molecules.The main research contents are as follows:?1?Two novel non-aromatic ring radical fullerene derivative acceptors were synthesized,including cyclohexanone-based fullerene derivative(CHOC₆₀)and cyclohexyl acetate-based fullerene derivative(CHAC₆₀).The preparation of CHOC₆₀ needs only one step simple Diels-Alder addition reaction.After reduction and esterification with high yield,CHOC₆₀ was further converted into CHAC₆₀.When the mass ratio of CHOC₆₀ and poly?3-hexylthiophene??P3HT?is 0.5:1,the PCE of PSC is 2.97%,but when the mass ratio of CHAC₆₀ and P3 HT is 0.5:1,the PCE of PSC is only 0.94%,the PCE is the highest up to 3.15% until the mass ratio is 1.5:1.Cyclohexanone-based acceptor is beneficial to reduce the preparation cost compared to cyclohexyl acetate-based acceptor.?2?Two new non-conjugated organic small-molecule zwitterion cathode interfacial materials containing sulfonic acid group were synthesized.They could reduce the charge transfer barrier and enhance the charge extraction owing to their dipole moment at the interface,leading to the high currents of the devices.The PCE of PSCs is up to 9.79% under the co-action of the interlayer and methanol-treated active layer.Moreover,the introduction of sulfonic acid groups not only increases the solubility of the materials in the water/alcohol reagent,but also does not damage the stability of the PSCs.?3?Two tetraphenylethylene-based molecules with aggregation induced emission?AIE?as cathode interfacial materials have been developed.Conjugated molecules with AIE effect usually has a twisted conformation and diffcultly forms the good ?-? stacking which is different from the traditional planar conjugated cathode interfacial materials.But they could also form the dipoles at the interface and effectively collect and transmit electron,causing the high currents of the devices.The highest PCE of the devices is up to 8.94%.?4?A series of benzophenone-based small molecular cathode interfacial materials with different polar end groups including hydroxyl group,neutral amino group,amino N-oxide,and sulfobetaine ion were synthesized,and the difference of the interfacial properties and photovoltaic properties of molecules with different functional groups were analyzed.Compared with the hydroxyl molecule,amino molecules have a larger interfacial dipole and better properties of electron extraction and transport,and stronger modification ability to both the work function of metal electrode and the surface potential of the active layer.Hereinto,amino N-oxide molecule has the best overall performance and the highest PCE of 9.34%,open-circuit voltage of 0.76 V,short-circuit current density of 17.09 m A/cm2,fill factor of 71.58%.This provides a reference for the design of excellent cathode interfacial materials.Through the study on the synthesis and properties of novel acceptors and cathode interfacial materials,the PCEs of PSCs are improved and the preparation cost of PSCs is decreased.It has made some exploratory research for the development of PSCs.