College of Chemistry and Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University , Xiangtan 411105, China.
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
ACS Appl Mater Interfaces. 2017 Feb 8;9(5):4614-4625. doi: 10.1021/acsami.6b14114. Epub 2017 Jan 30.
Three acceptor-π-donor-π-acceptor (A-π-D-π-A) small molecules (STFYT, STFRDN, and STFRCN) with spiro[cyclopenta[1,2-b:5,4-b']dithiophene-4,9'-fluorene] (STF) as the central donor unit, terthiophene as the π-conjugated bridge, indenedione, 3-ethylrhodanine, or 2-(1,1-dicyanomethylene)rhodanine as the acceptor unit are designed, synthesized, and characterized as electron donor materials in solution-processing organic solar cells (OSCs). The effects of the spiro STF-based central core and different acceptors on the molecular configuration, absorption properties, electronic energy levels, carrier transport properties, the morphology of active layers, and photovoltaic properties are investigated in detail. The three molecules exhibit desirable physicochemical features: wide absorption bands (300-850 nm) and high molar absorption coefficients (4.82 × 10 to 7.56 × 10 M cm) and relatively low HOMO levels (-5.15 to -5.38 eV). Density functional theory calculations reveal that the spiro STF central core benefits to reduce the steric hindrance effect between the central donor block and terthiophene bridge and suppress excessive intermolecular aggregations. The optimized OSCs based on these molecules deliver power conversion efficiencies (PCEs) of 6.68%, 3.30%, and 4.33% for STFYT, STFRDN, and STFRCN, respectively. The higher PCE of STFYT-based OSCs should be ascribed to its better absorption ability, higher and balanced hole and electron mobilities, and superior active layer morphology as compared to the other two compounds. So far, this is the first example of developing the A-π-D-π-A type small molecules with a spiro central donor core for high-performance OSC applications. Meanwhile, these results demonstrate that using spiro central block to construct A-π-D-π-A molecule is an alternative and effective strategy for achieving high-performance small molecule donor materials.
三种具有螺环[环戊[1,2-b:5,4-b']二噻吩-4,9'-芴]（STF）作为中心供体单元、噻吩作为π共轭桥、茚二酮、3-乙基罗丹宁或 2-(1,1-二氰基亚甲基)罗丹宁作为受体单元的受体-π-供体-π-受体（A-π-D-π-A）小分子（STFYT、STFRDN 和 STFRCN）被设计、合成并作为电子供体材料在溶液处理的有机太阳能电池（OSC）中进行了表征。详细研究了基于螺环 STF 的中心核和不同受体对分子构型、吸收性质、能级、载流子输运性质、活性层形貌和光伏性能的影响。这三种分子表现出理想的物理化学特性：宽吸收带（300-850nm）和高摩尔吸光系数（4.82×10 到 7.56×10 M cm）和相对较低的 HOMO 能级（-5.15 到-5.38 eV）。密度泛函理论计算表明，螺环 STF 中心核有利于降低中心供体块与噻吩桥之间的空间位阻效应，并抑制过度的分子间聚集。基于这些分子的优化 OSC 分别提供了 6.68%、3.30%和 4.33%的功率转换效率（PCE）。STFYT 基 OSC 的较高 PCE 应归因于与其他两种化合物相比，其具有更好的吸收能力、更高和平衡的空穴和电子迁移率以及更优的活性层形貌。到目前为止，这是首例以螺环中心供体核为基础开发用于高性能 OSC 应用的 A-π-D-π-A 型小分子的例子。同时，这些结果表明，使用螺环中心块构建 A-π-D-π-A 分子是实现高性能小分子供体材料的一种替代且有效的策略。
