Ammonium Salt-Containing And Cyanoacetic Acid-Containing Conjugated Polyelectrolytes: Design, Synthesis And Properties

Polymer solar cells provide the combined attraction of low cost, light weight andmechanical flexibility. As a result, polymer solar cells have become a highlightresearch area in recent years. As for the power converstion efficiency aspect, progresshas been impressive, yet there are still many problems in the published researchpapers and there is still much to do before the realization of practical applications ofpolymer solar cells. For example, the Voc value is often reported to be relatively lowdue to non-ohamic contact between the metal electrode and the active layer. LiF isone of the commonly used interfacial layer materials. However, thermal deposition ofLiF in a vacuum is not well-suited for all-solution processing.Conjugated polyelectrolytes are often readily dissolved in high polar solvents,such as alcohol and water. On the one hand, alcohol and water areenvironmental-friendly solvents, and they exhibit low toxicity to pet, person andenvironment. On the other hand, good solubility in high polar solvents can avoiderosion of the subsequent layers during multilayer integration. Thus, conjugatedpolyelectrolytes are considered to be good candidates for the interfacial layermaterials in optoelectronic devices. They have been successfully used in organicoptoelectronic devices, providing plenty of positive and meaningful results. Utilizingconjugated polyelectrolytes as interfacial layer materials wasn’t proposed until recentyears, thus there are still plenty of problems crying out for solutions within thisresearch field. For example, the structural diversity of the used conjugatedpolyelectrolytes as interfacial layer materials is still limited. We designed twopolymeric systems of conjugated polyelectrolytes, and selected one target polymer toserve as interfacial layer material in polymer solar cells. The work content is as follows:1. Three conjugated polyelectrolytes, named PFBT-Br20，PFBT-Br80，PFBT-Br100, were synthesized by Suzuki coupling reaction and quaternization reaction.P3HT:PC₆₁BM based polymer solar cells were fabricated by using PFBT-Br100asinterfacial layer material. The incorporation of PFBT-Br100interfacial layer greatlyincreased the Voc of the resulting device, which exhibited high power conversationefficiencies, comparable to those achieved by LiF-modified devices.2. We successfully synthesized three conjugated polyelectrolytes, named PF-TPA,PCz-TPA and PBDT-TPA by Suzuki and Stille coupling reactions, as well asKnoevenagel condensation reaction. The incorporation of cyanoacetic acid in to theseconjugated polyelectrolytes endows them good solubility in high polar solvents, suchas DMAc and DMF. This unique property facilitates the fabrication of multilayerdevices. Three conjugated polyelectrolytes all exhibited low-lying HOMO energylevels, indicating that they can serve as cathode modification layer for photovoltaicdevices, as the hole-blocking layer.