光交联型窄带隙共聚物的合成及其对本体异质结聚合物太阳电池稳定性的影响

Synthesis of photocrosslinkable low-bandgap copolymers and their effect on the stability of bulk heterojunction polymer solar cells

本体异质结聚合物太阳电池的活性层通常是由聚合物给体和富勒烯受体通过机械混合而成,活性层的聚合物和富勒烯分子从热力学角度倾向于各自聚集,由此形成的纳米微相分离结构是热不稳定的,造成电池稳定性较差。为了提高活性层薄膜形貌稳定性,本文设计并合成出新型的溴基团取代的光交联型窄带隙聚合物PBDTTT-Br25和PBDTTT-Br50。经光引发交联后的聚合物薄膜表现出良好的抗溶剂性和形貌稳定性,且不影响聚合物分子排列及载流子传输性能。通过研究热退火对共混膜形貌的影响,发现使用光交联材料可以有效抑制富勒烯分子聚集,并提高聚合物太阳电池的热稳定性。基于PBDTTT-Br25和PBDTTT-Br50的器件光电转换效率分别为5.17%和4.48%,相比于基于聚合物PBDTTT的器件效率(4.26%),性能得到明显的提高。

The active layer of bulk heteroj unction polymer solar cells is usually prepared by mechanical blending of polymer donors and fullerene acceptors.The polymer or fullerenes in the blend layer prefers to segregate from each other thermodynamically;therefore,the phase-separated nanostructure of the active layer is thermally unstable,which increases the instability of the PSCs. To stabilize the film morphology of the active layer,novel bromine-functionalized photocrosslinkable low-bandgap copolymers, PBDTTT-Br25 and PBDTTT-Br50 are designed and synthesized.The photo-crosslinked polymer films exhibit excellent solvent resistance and thermal morphology stability,and the photoinitiation process shows minimal effect on the packing of conj ugated polymers and electronic properties.The formation of large aggregations of fullerene is suppressed even after prolonged thermal annealing,and the stability of the device is enhanced.The power conversion efficiency of the PBDTTT-Br25-based and PBDTTT-Br50-based PSCs reaches 5.17%and 4.48%,respectively,which is much higher than that （4.26%）of the PBDTTT-based de-vice.