Correa Roger S, Santos Bianca P S, Ribeiro Arthur C, da Silva Luiz Alberto F, Péan Emmanuel V, Davies Matthew L, Marques Maria de Fátima V, Rocco Maria Luiza M
Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, 21941-909, Rio de Janeiro, Brazil.
Instituto de Macromoléculas Professora Eloisa Mano (IMA), Universidade Federal do Rio de Janeiro, Cidade Universitária, 21941-598, Rio de Janeiro, Brazil.
Phys Chem Chem Phys. 2022 Jul 27;24(29):17852-17861. doi: 10.1039/d2cp01474b.
Several strategies have been considered in search of more efficient organic materials for charge transfer in photovoltaic devices. Among them, the integration of donor-acceptor (D-A) functional units on a conjugated copolymer has been widely applied. In this framework, we evaluated four terpolymers made up of donor moieties derived from 9,9-dioctylfluorene and 9-(heptadecan-9-yl)-9-carbazole combined with 2,1,3-benzothiadiazole, the acceptor moiety, in different monomer ratios and polymerization routes (block and random microstructures). The preferred molecular orientation and charge transfer dynamics of the polymeric films were assessed by near edge X-ray absorption fine structure spectroscopy (NEXAFS) and resonant Auger electron spectroscopy (RAES) around the sulfur K-edge. Charge transfer times () were estimated by the Core-Hole Clock (CHC) method. Films with a high degree of organization were identified for the block terpolymer and random terpolymers with uneven amounts of donor units, showing a preferred orientation of the benzothiadiazole (BT) molecular plane parallel to the substrate surface. The values of measured for all terpolymers were higher than those for typical polymers used in photovoltaic devices, which is not desirable for this type of optoelectronic application, but this may be correlated to the strong acceptor character of BT, the unit probed. To investigate the effect of film formation on the excited state behavior, steady-state and time-resolved photoluminescence measurements were also conducted. X-ray photoelectron spectroscopy (XPS) was employed to characterize the surface chemical composition of the terpolymer films. Based on the spectroscopic data the block copolymer appears to be the most suitable for the desired application.
为了寻找用于光伏器件中电荷转移的更高效有机材料，人们考虑了几种策略。其中，给体-受体（D-A）功能单元在共轭共聚物上的整合已得到广泛应用。在此框架下，我们评估了四种三元共聚物，它们由源自9,9-二辛基芴和9-(十七烷-9-基)-9-咔唑的给体部分与受体部分2,1,3-苯并噻二唑以不同的单体比例和聚合路线（嵌段和无规微结构）组合而成。通过硫K边附近的近边X射线吸收精细结构光谱（NEXAFS）和共振俄歇电子能谱（RAES）评估了聚合物薄膜的优选分子取向和电荷转移动力学。电荷转移时间（）通过核空穴时钟（CHC）方法估算。对于嵌段三元共聚物和给体单元数量不均的无规三元共聚物，鉴定出具有高度有序性的薄膜，其显示出苯并噻二唑（BT）分子平面平行于基底表面的优选取向。所有三元共聚物测得的 值均高于光伏器件中使用的典型聚合物的值，这对于此类光电子应用而言是不理想的，但这可能与所探测的单元BT的强受体特性相关。为了研究成膜对激发态行为的影响，还进行了稳态和时间分辨光致发光测量。采用X射线光电子能谱（XPS）表征三元共聚物薄膜的表面化学成分。基于光谱数据，嵌段共聚物似乎最适合所需的应用。
