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Efficient light-harvesting, energy migration, and charge transfer by nanographene-based nonfullerene small-molecule acceptors exhibiting unusually long excited-state lifetime in the film state
Chemical Science ( IF 7.6 ) Pub Date : 2020/03/05 , DOI: 10.1039/c9sc06456g
Tomokazu Umeyama 1, 2, 3, 4, 5 , Kensho Igarashi 1, 2, 3, 4, 5 , Daiki Sasada 1, 2, 3, 4, 5 , Yasunari Tamai 2, 3, 4, 5, 6 , Keiichi Ishida 1, 2, 3, 4, 5 , Tomoyuki Koganezawa 5, 7 , Shunsuke Ohtani 2, 3, 4, 5, 6 , Kazuo Tanaka 2, 3, 4, 5, 6 , Hideo Ohkita 2, 3, 4, 5, 6 , Hiroshi Imahori 1, 2, 3, 4, 5
Affiliation  

Electron-acceptor small-molecules possessing a long exciton lifetime and a narrow energy band gap, opposing the energy gap law, are highly desirable for high-performance organic photovoltaics (OPVs) by realizing their efficient light-harvesting ability (LH), exciton diffusion (ED), and charge transfer (CT). Toward this goal, we designed an acceptor–donor–acceptor (A–D–A) type nonfullerene acceptor (NFA), TACIC, having an electron-donating, self-assembling two-dimensional (2D) nanographene unit, thienoazacoronene, at the center with electron-withdrawing groups at both ends. The TACIC film exhibited a narrow band gap (1.59 eV) with excellent LH. Surprisingly, the TACIC film showed an extremely long exciton lifetime (1.59 ns), suppressing undesirable nonradiative decay by its unique self-assembling behavior. When combined with a conjugated polymer donor, PBDB-T, slow ED and CT were observed (60 ps) with the excitation of TACIC owing to the large TACIC domain sizes. Nevertheless, the unusually high efficiencies of ED and CT (96% in total) were achieved by the long TACIC exciton lifetime. Additionally, unusual energy transfer (EnT) from the excited PBDB-T to TACIC was seen, demonstrating its dual LH role. The OPV device with PBDB-T and TACIC showed a high incident photon-to-current efficiency (IPCE) exceeding 70% at up to 710 nm and a power conversion efficiency of ∼10%. This result will open up avenues for a rational strategy of OPVs where LH, ED, and CT from the acceptor side as well as LH, EnT, ED, and CT from the donor side can be better designed by using 2D nanographene as a promising building block for high-performance A–D–A type NFAs.

中文翻译:

基于纳米石墨烯的非富勒烯小分子受体的高效光捕获,能量迁移和电荷转移,在膜态下表现出异常长的激发态寿命

与激子寿命定律相反,具有长激子寿命和窄能带隙的电子受体小分子,通过实现高效的光收集能力(LH),激子扩散,对于高性能有机光伏(OPV)来说是非常理想的(ED)和电荷转移(CT)。为了实现这一目标,我们设计了一种受主-供主-受主(A–D–A)型非富勒烯受体(NFA)TACIC,在其表面具有供电子的,自组装的二维(2D)纳米石墨烯单元,硫杂氮杂壬烯。两端带有吸电子基团。TACIC膜显示出窄带隙(1.59 eV)和出色的LH。令人惊讶的是,TACIC膜表现出极长的激子寿命(1.59 ns),通过其独特的自组装行为抑制了不良的非辐射衰减。当与共轭聚合物供体结合时,由于TACIC结构域尺寸大,在TACIC激发下观察到PBDB-T,慢速ED和CT(60 ps)。尽管如此,由于TACIC激子寿命长,ED和CT的效率异常高(总计96%)。此外,还发现了从激发的PBDB-T到TACIC的异常能量转移(EnT),表明了其双重LH作用。具有PBDB-T和TACIC的OPV器件在高达710 nm处显示出超过70%的高入射光子-电流效率(IPCE),功率转换效率约为10%。该结果将为OPV的合理策略开辟道路,其中可以通过使用二维纳米石墨烯作为有前途的建筑来更好地设计受体侧的LH,ED和CT以及供体侧的LH,EnT,ED和CT高性能A–D–A型NFA的模块。由于TACIC域较大,在TACIC激发下观察到了缓慢的ED和CT(60 ps)。尽管如此,由于TACIC激子寿命长,ED和CT的效率异常高(总计96%)。此外,还发现了从激发的PBDB-T到TACIC的异常能量转移(EnT),表明了其双重LH作用。具有PBDB-T和TACIC的OPV器件在高达710 nm处显示出超过70%的高入射光子-电流效率(IPCE),功率转换效率约为10%。该结果将为OPV的合理策略开辟道路,其中可以通过使用二维纳米石墨烯作为有前途的建筑来更好地设计受体侧的LH,ED和CT以及供体侧的LH,EnT,ED和CT高性能A–D–A型NFA的模块。由于TACIC域较大,在TACIC激发下观察到了缓慢的ED和CT(60 ps)。尽管如此,由于TACIC激子寿命长,ED和CT的效率异常高(总计96%)。此外,还发现了从激发的PBDB-T到TACIC的异常能量转移(EnT),表明了其双重LH作用。具有PBDB-T和TACIC的OPV器件在高达710 nm处显示出超过70%的高入射光子-电流效率(IPCE),功率转换效率约为10%。该结果将为OPV的合理策略开辟道路,其中可以通过使用二维纳米石墨烯作为有前途的建筑来更好地设计受体侧的LH,ED和CT以及供体侧的LH,EnT,ED和CT高性能A–D–A型NFA的模块。
更新日期:2020-03-26
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