Bassi Maiara de Jesus, Benatto Leandro, Wouk Luana, Holakoei Soheila, Oliveira Camilla Karla, Rocco Maria Luiza M, Roman Lucimara Stolz
Department of Physics, Federal University of Paraná, Curitiba 81531-980, Paraná, Brazil.
Phys Chem Chem Phys. 2020 Sep 21;22(35):19923-19931. doi: 10.1039/d0cp02520h. Epub 2020 Aug 28.
In this study, we investigate two copolymers as electron donors in photovoltaic devices, PFO-DBT (poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole]) and its analogue with Si, PSiF-DBT (poly[2,7-(9,9-dioctyl-dibenzosilole)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole]). The results discussed here are related to the influence of heavy atoms on the electrical and morphological properties of the devices. Charge transfer dynamics in the polymeric films were evaluated using the core-hole clock method. Besides that, using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, we investigate the electronic structure and charge transfer properties of the two systems. The charge transfer rates were estimated in the framework of the semiclassical Marcus/Hush theory. We found that the better stacking between the polymer chains for PSiF-DBT provides higher solar absorption capacity in regions of higher wavelengths and faster hole transfer rates. We also obtain a faster electron transfer rate at the PSiF-DBT/C interface compared to the PFO-DBT/C interface that is mainly related to the difference in the driving force between the two systems. These features help to explain why the organic photovoltaic devices using PSiF-DBT as the active layer exhibited a higher performance compared to devices using PFO-DBT. Here, we show that our results are able to provide important insights about the parameters that can influence the photovoltaic performance of the devices.
在本研究中，我们研究了两种共聚物作为光伏器件中的电子供体，即PFO-DBT（聚[2,7-(9,9-二辛基芴)-alt-4,7-双(噻吩-2-基)苯并-2,1,3-噻二唑]）及其含硅类似物PSiF-DBT（聚[2,7-(9,9-二辛基二苯并硅氧烷)-alt-4,7-双(噻吩-2-基)苯并-2,1,3-噻二唑]）。这里讨论的结果与重原子对器件电学和形态学性质的影响有关。使用芯孔时钟法评估了聚合物薄膜中的电荷转移动力学。除此之外，我们使用密度泛函理论（DFT）和含时DFT（TD-DFT）方法，研究了这两个体系的电子结构和电荷转移性质。在半经典Marcus/Hush理论框架内估计了电荷转移速率。我们发现，PSiF-DBT的聚合物链之间更好的堆积在更高波长区域提供了更高的太阳能吸收能力和更快的空穴转移速率。与PFO-DBT/C界面相比，我们在PSiF-DBT/C界面也获得了更快的电子转移速率，这主要与两个体系之间驱动力的差异有关。这些特性有助于解释为什么使用PSiF-DBT作为活性层的有机光伏器件比使用PFO-DBT的器件表现出更高的性能。在此，我们表明我们的结果能够为影响器件光伏性能的参数提供重要见解。
