Design of a thiophene-fused benzotriazole unit as an electron acceptor to build D-A copolymers for polymer solar cells
Design of a thiophene-fused benzotriazole unit as an electron acceptor to build D-A copolymers for polymer solar cells
复制标题
噻吩稠合苯并三唑单元作为电子受体的设计，用于构建聚合物太阳能电池的 D-A 共聚物
DOI：
10.1039/c7tc00083a
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发表时间：
2017
影响因子：
6.4
通讯作者：
Li Yongfang
中科院分区：
文献类型：
--
作者：
Zhou Pengcheng;Yang Yang;Chen Xingguo;Zhang Zhi Guo;Li Yongfang
首次设计了一种新型电子受体噻吩稠合苯并三唑（BTAZT），以联噻吩取代的苯并[1,2-b:4,5-b']二噻吩（BDTT）作为聚合物太阳能电池（PSC）的电子给体单元构建供体-受体共聚物。与含有类似共轭主链但以苯并三唑（BTAZ）单元作为受体的类似聚合物相比，基于BTAZT的聚合物表现出明显的红移吸收和更窄的光学带隙，这是由于噻吩部分融合到BTAZ单元上以进一步稳定其共轭主链的醌型结构。此外，引入两种类型的侧链基团，即烷基羧基（在PBDTT-BTAZT-1中）或烷基羰基（在PBDTT-BTAZT-2中）来调节能量水平并调节PBDTT-BTAZT基聚合物的溶解度。研究发现，稠合噻吩α位烷基羧基相对于烷氧羰基具有更强的吸电子能力，可以进一步降低HOMO能级，从而提高PBDTT-BTAZT-2器件的开路电压（Voc）。制备了基于这两种聚合物作为电子给体材料和富勒烯衍生物（PC71BM）作为电子接受材料的PSC器件，并研究了使用添加剂（DIO或NMP）来修改活性层和阴极缓冲层（PDIN或PDINO）的形貌以修改阴极中间层的器件优化。使用 DIO 添加剂和 PDIN 改性阴极中间层的基于 PBDTT-BTAZT-1 的器件获得了约 7% 的最佳 PCE。值得注意的是，其最佳短路电流密度达到 14.41 mA cm−2，这是具有 PCBM 受体的基于 BTAZ 的 PSC 中报道的最高值之一。使用NMP添加剂和PDINO改性阴极中间层时，基于PBDTT-BTAZT-2的器件的最佳PCE也达到6.16%。
A new electron-acceptor, thiophene-fused benzotriazole (BTAZT), is designed for the first time to construct donor–acceptor copolymers with bithienyl substituted benzo[1,2-b:4,5-b′]dithiophene (BDTT) as an electron-donor unit for polymer solar cells (PSCs). Compared with their analogous polymers, which contain a similar conjugated backbone but with the benzotriazole (BTAZ) unit as the acceptor, the BTAZT-based polymers show evident red-shifted absorption with narrower optical band gaps due to the fusion of the thiophene moiety onto the BTAZ unit to further stabilize the quinoid structure of their conjugation backbones. Furthermore, two types of side-chain groups, the alkylcarboxyl group (in PBDTT-BTAZT-1) or alkylcarbonyl group (in PBDTT-BTAZT-2), are introduced to adjust the energy levels and modulate the solubility of the PBDTT-BTAZT based polymers. It is found that the stronger electron-withdrawing ability of the alkylcarboxyl group relative to that of the alkoxycarbonyl group at the α-position of the fused thiophene can further reduce the HOMO energy level to enhance the open voltage (Voc) in the PBDTT-BTAZT-2 based device. PSC devices based on these two polymers as electron-donating materials and a fullerene derivative (PC71BM) as an electron-accepting material are fabricated, and device optimization with additives (DIO or NMP) to modify the morphologies of the active layers and cathode buffer layers (PDIN or PDINO) to modify the cathode interlayers is investigated. The best PCE of approximately 7% is obtained for the PBDTT-BTAZT-1 based device with the DIO additive and PDIN-modified cathode interlayer. Notably, its optimal short circuit current density reaches 14.41 mA cm−2, which is one of the highest values ever reported in BTAZ-based PSCs with a PCBM acceptor. The best PCE of the PBDTT-BTAZT-2 based device also reaches 6.16% with the NMP additive and PDINO-modified cathode interlayer.