| 초록 |
Molecular weight has affected to significant properties of conjugated polymers including crystallinity, solubility of organic solvents which are essential for determining performance of all-polymer solar cells. Here in, a series of n-type naphthalene diimide bithiophene copolymers (P(NDI2HD-T2)) with different molecular weights (PL, PM, PH; Mn = 14, 23, 50 kg/mol) were synthesized. Their electrical, structural and photovoltaic properties were investigated. Particularly, the PH film preferred face-on oriented packing, while the PL film favored edge-on directed packing. In detail, their relative numerical face-on fraction were enhanced from 17, 36, to 66% for PL, PM, and PH. The face-on orderings of PH shorten the geminate recombination arisen from conflict of orientation between donor and acceptor. Finally, improved charge dissociation and transport of optimized device of PH with donor PTB7-Th lead to high power conversion efficiency 6.14% compared to 4.29% of PL without additive. |
