| 초록 |
Branching point of side chain in naphthalene diimide (NDI)-based polymers was systematically shifted away one by one (from P(NDI1-T) to P(NDI4-T)). When the branching point was located farther from backbone, steric hindrance around backbone was relaxed and promoted the formation of crystalline structure in thin film state. Particularly, thermally annealed films of P(NDI3-T) and P(NDI4-T) which have branching point far away from backbone showed more-ordered bimodal structure along face-on and edge-on directions. Consequently, field-effect electron mobility was monotonically increased from 0.03 cm2 V−1 s−1 to 0.22 cm2 V−1 s−1 with reduced activation energy and contact resistance. When the series of polymers was applied in all-polymer solar cell, the highest power conversion efficiency of 7.1% was achieved in P(NDI3-T) blend film with PBDTTTPD as a donor due to broader light absorption ability and enhanced electron transporting ability of P(NDI3-T). |
