Effects of the rigid and sterically bulky structure of non-fused nonfullerene acceptors on transient photon-to-current dynamics,Journal of Materials Chemistry A

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Effects of the rigid and sterically bulky structure of non-fused nonfullerene acceptors on transient photon-to-current dynamics
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2022-08-09 , DOI: 10.1039/d2ta02604j
Seihou Jinnai ₁ , Kasumi Murayama ₂ , Keisuke Nagai ₁ , Megumi Mineshita ₃ , Kosaku Kato ₄ , Azusa Muraoka ₃ , Akira Yamakata ₄ , Akinori Saeki _{5,

6} , Yasuhiro Kobori _{2,

7} , Yutaka Ie _{1,

6}

Affiliation

Non-fused electron-accepting π-conjugated compounds have been investigated recently for application to nonfullerene acceptors (NFAs) in organic solar cells (OSCs). However, the establishment of rational molecular design for non-fused NFAs is still lagging because the influence of flexible non-fused structures on the dynamics of electron–hole pairs in OSCs is not entirely understood. In this study, we utilized cyclopentene-annelated thiophene with spiro-substituted 2,7-bis(2-ethylhexyl)fluorene (FT) as a rigid and sterically bulky linker unit and developed a non-fused NFA (TT–FT–DCI) containing FT units. Photophysical measurements indicated that the introduction of the FT unit leads to the formation of rigid molecular structure. OSCs based on donor polymer (PBDB-T) and TT–FT–DCI showed an improved power conversion efficiency of 7.13% due to the increase in the short-circuit current density and fill factor. Time-resolved optical and microwave spectroscopies showed that the FT unit contributes to the long lifetimes of excited state and charge-separated state in the PBDBT:TT–FT–DCI blend films. Time-resolved electron paramagnetic resonance measurements showed that the distant charge-separated states of the face-to-face PBDB-T:TT–FT–DCI structure, which is derived by avoiding over-crystallization by the steric bulkiness of TT–FT–DCI, can interact with the cathodes for preferential electron injection following charge generations. This study highlights that by using the rigid π-conjugated framework and suppressed self-aggregation of the non-fused acceptor, effective molecular design for the appropriate dynamics of photocurrent generation is possible.

中文翻译：

非稠合非富勒烯受体的刚性和空间庞大结构对瞬态光子电流动力学的影响

最近研究了非稠合电子接受 π- 共轭化合物用于有机太阳能电池 (OSC) 中的非富勒烯受体 (NFA)。然而，非融合 NFA 的合理分子设计的建立仍然滞后，因为柔性非融合结构对 OSC 中电子-空穴对动力学的影响尚不完全清楚。在这项研究中，我们利用环戊烯化噻吩和螺取代的 2,7-双（2-乙基己基）芴（FT）作为刚性和空间庞大的连接单元，并开发了非稠合 NFA（TT-FT-DCI）包含 FT 单位。光物理测量表明，FT单元的引入导致了刚性分子结构的形成。基于供体聚合物 (PBDB-T) 和 TT-FT-DCI 的 OSC 的功率转换效率提高了 7。13% 由于短路电流密度和填充因子的增加。时间分辨光学和微波光谱表明，FT 单元有助于延长 PBDBT:TT-FT-DCI 共混膜中激发态和电荷分离态的寿命。时间分辨电子顺磁共振测量表明，面对面的 PBDB-T:TT-FT-DCI 结构的远电荷分离状态是通过 TT-FT-的空间体积避免过度结晶而得出的。 DCI 可以与阴极相互作用，以便在产生电荷后优先注入电子。该研究强调，通过使用刚性 π 共轭框架和抑制非融合受体的自聚集，可以为适当的光电流产生动力学设计有效的分子。

更新日期：2022-08-09

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