Department of Nanofusion Technology (BK21) and Cogno-Mechatronics Engineering (WCU), Pusan National University, Miryang 627-706, Republic of Korea.
Chemistry. 2012 Feb 27;18(9):2551-8. doi: 10.1002/chem.201102883. Epub 2012 Jan 25.
A low-band-gap alternating copolymer, poly{5,6-bis(octyloxy)-4-(thiophen-2-yl)benzo[c]-1,2,5-thiadiazole} (PTBT), was synthesized and investigated for photovoltaic applications. PTBT showed a minimized torsion angle in its main backbone owing to the introduction of solubilizing octyloxy groups on the electron-poor benzothiadiazole unit, thereby resulting in pronounced intermolecular ordering and a deep level of the HOMO (-5.41 eV). By blending PTBT with [6,6]phenyl-C61-butyric acid methyl ester (PC(61)BM), highly promising performance was achieved with power-conversion efficiencies (PCEs) of 5.9 and 5.3% for the conventional and inverted devices, respectively, under air mass 1.5 global (AM 1.5G, 100 mW cm(-2)) illumination. The open-circuit voltage (V(OC) ≈ 0.85-0.87 V) is one of the highest values reported thus far for thiophene-based polymers (e.g., poly(3-hexylthiophene) V(OC) ≈ 0.6 V). The inverted device also achieved a remarkable PCE compared to other devices based on low-band-gap polymers. Ideal film morphology with bicontinuous percolation pathways was expected from the atomic force microscopy (AFM) images, space-charge-limited current (SCLC) mobility, and selected-area electron-diffraction (SAED) measurements. This molecular design strategy is useful for achieving simple, processable, and planar donor-acceptor (D-A)-type low-band-gap polymers with a deep HOMO for applications in photovoltaic cells.
一种低带隙交替共聚物，聚{5,6-双（辛氧基）-4-（噻吩-2-基）苯并[c]-1,2,5-噻二唑}（PTBT），被合成并研究了其在光伏应用中的性能。PTBT 在其主链中引入了可溶的辛氧基基团，使电子贫乏的苯并噻二唑单元的扭转角最小化，从而导致明显的分子间有序性和 HOMO 能级（-5.41 eV）的加深。通过将 PTBT 与[6,6]-苯基-C61-丁酸甲酯（PC（61）BM）共混，在空气体 1.5 全球（AM 1.5G，100 mW cm（-2））照射下，常规和倒置器件的功率转换效率（PCE）分别达到了 5.9%和 5.3%，性能非常出色。开路电压（V（OC）≈0.85-0.87 V）是迄今为止报道的基于噻吩的聚合物中最高的值之一（例如，聚（3-己基噻吩）V（OC）≈0.6 V）。与其他基于低带隙聚合物的器件相比，倒置器件的 PCE 也取得了显著的提高。原子力显微镜（AFM）图像、空间电荷限制电流（SCLC）迁移率和选区电子衍射（SAED）测量表明，预期具有理想的薄膜形态和双连续渗流途径。这种分子设计策略对于实现简单、可加工、平面的给体-受体（D-A）型低带隙聚合物是有用的，这些聚合物具有深的 HOMO，可用于光伏电池。
