Synthesis Of Narrow Band-gap Conjugated Polymers And The Investigation Of Photovoltaic Performance

Inexhaustible supply, clean and friendly to environment which make solar energy become one of the most significant ways to solve the global energy shortage. Solar energy can be converted directly into electrical energy that make it becoome a research hot spot in recent years and draw a lot of attention.Solar cells can be divided into two major categories:inorganic solar cells and organ-ic solar cells. Inorganic solar cells (mainly silicon-based solar cells) have occupied the market through years’hard work. However, high cost, complexity in fabrication technol-ogy and toxic foreshadow that inorganic solar cells encounter bottleneck.Unlike inorganic solar cells, owing to low-cost, flexible, large-area film formation and environment friendly, polymer solar cells (PSCs) have become a new research direc-tion. After several years’technology and experience accumulating, power conversion effi-ciency (PCE) of PSCs are over 10%, but the stability of PSCs which is the main obstacle remains to be solved for commercialization.PSCs based on classical polythiophene have a PCE over 5%, bandgap lower than 2.0 eV which result in a absorption of sunlight less than 650 nm, while main sunlight energy is concentrated in 700 nm. D-A (donor-acceptor) type conjugated polymer can reduce bandgap obviously. Because of push and pull electron effect, the BLA value can be de-creased significantly. According to Molecular Orbital Hybridization Theory, electrons are reassigned to the hybrid polymer molecular orbitals. Finally, a higher HOMO and lower LUMO levels are formed. The bandgap decreasing strongly dependents on the strength of push-pull effect, so it is key to select appropriate donor and acceptor unit.This paper reviewed the development of a part of donor materials, designed and syn-thesized five D-A copolymers based on donor unit like BDT, fluorene, carbazole and ac-ceptor unit such as DPP and benzopyrazine. P1, P2 and P3 synthesized through Stille coupling and P4 and P5 through direct arylation polymerization.The structures of polymers were tested by IR, GPC and 1H NMR. The thermal stabil-ity, optical property and electrochemical property were investigated by TGA, DSC, UV- Vis, PL and CV. PSCs (P1-P5 as donor materials) were made. The performance were strengthened through optimization.