Synthesis Of Novel Organic Molecules Based On Thienopyrroledione For All-Polymer Solar Cell

In recent years,organic solar cells have developed rapidly under the efforts of many researchers.All-polymer solar cells?All-PSCs?have attracted much attention due to their unique features,such as low cost,light weight,flexibility,large area device fabrication and good stability.The materials of All-PSCs mainly include p-type polymer donors and n-type polymer acceptors.The most widely reported p-type polymer donors are benzodithiophene?BDT?-based polymer donor materials,which have inherent properties,such as high hole mobility,rigid plane,ordered molecular packing,broad light absorption,and adjustable energy levels.At present,improving the power conversion efficiency of all-polymer solar cells is a key issue in the research of all-polymer solar cells,and the compatibility and matching with polymer donors and acceptors are also important issues in improving the power conversion efficiency.In order to obtain all-polymer solar cells with high power conversion efficiency,looking for materials with superior performance by means of physical blending and chemical copolymerization based on the reported polymer PBDTTPD/P?NDI2HD-T?systems.In this paper,small organic molecule TPD-X based on thienopyrroledione?TPD?with different electron-withdrawing groups were designed and synthesized.Then,we introduced different amounts of small organic molecule materials into the polymer PBDTTPD/P?NDI2HD-T?systems to assembled all-polymer solar cell.Meanwhile,a series of?D?_a-?A?_b random polymer donor materials were obtained from chemical copolymerization by adjusted the component between the donor unit and the acceptor unit in the polymer donor.The material selection and device preparation process optimization were carried out.For obtain all-polymer solar cells with high performance.This paper has carried out the following work:1.TPD-RD,TPD-AC,and TPD-CN were synthesized by Knoevenagel condensation reaction.Three small organic molecules were characterized by NMR,MS,UV-Vis and CV.Polymer solar cells were prepared by physical blending of three small organic molecule with different contents into the polymer PBDTTPD/P?NDI2HD-T?systems.When the doping amount was 3%,the device performance of the three small organic molecules shown the best,and power conversion efficiencies shown 4.08%,3.86%and2.65%,respectively.These results suggested that the energy levels of TPD-RD and TPD-AC are compatible and appropriated crystallization with the PBDTTPD.Hence,TPD-RD and TPD-AC are more suitable as dopants for the PBDTTPD/P?NDI2HD-T?system.2.A series of?D?a-?A?b random P?BDT?_a?TPD?_b donor materials were synthesized by Stille coupling reaction with tuned the content of benzodithiophene?BDT?and thienopyrroledione?TPD?.The polymers were characterized by NMR,GPC,CV,UV-Vis,DSC and XRD.The results showed that with the increase of BDT unit content,the regularity of D-A orderly alternating polymer was destroyed,the solubility of the polymer was improved and had good solubility in green solvent?methyl tetrahydrofuran?.Meanwhile,due to the increase of BDT unit content,the light absorption of P?BDT?_a?TPD?_b donor materials significantly blueshifted,which filled the absorption defects of the polymer PBDTTPD/P?NDI2HD-T?systems at 400-500 nm.This enhanced absorption at 400-500 nm while formed a good complementary absorption with polymer acceptor P?NDI2HD-T?.The HOMO and LUMO levels of polymers P?BDT?_a?TPD?_b slightly changed.The difference between HOMO and LUMO levels are greater than 0.3eV that rovided sufficient driving force to ensure effective exciton separation.In conclusion,random P?BDT?_a?TPD?_b were favorable polymer donor materials which treated with green-solvent to fabricated all-polymer solar cells.3.Devices were preliminarily prepared by random bi-copolymers P?BDT?_a?TPD?_b with P?NDI2HD-T?acceptor to screened out PBDTTPD,P?BDT?₈?TPD?₇,P?BDT?₅?TPD?₄ and P?BDT?₃?TPD?₂ whose power conversion efficiency exceeded 5%.The effects of device post-processing technology on device performance were explored to obtain the optimal condition for device preparation.The power conversion efficiency of devices showed 6.41%,5.95%,8.03%and 6.43%under the optimal condition.External quantum efficiency?EQE?,space charge limiting current?SCLC?and atomic force microscope?AFM?were used to study the optical response,mobility and morphology of the active layer.Furthermore,P?BDT?₅?TPD?₄/P?NDI-2HD-T?polymer system obtains thick film with high PCE under green non-halogen solvent,which is a new strategy for all-polymer solar cells to obtain high power conversion efficiency,low cost,environment friendly and film thickness insensitive.