化学学报 ›› 2012, Vol. 70 ›› Issue (22): 2365-2371.DOI: 10.6023/A12090635 上一篇    下一篇

研究论文

两种异质结太阳能电池聚合物供体材料的设计与理论性质

刘小锐, 陈春香, 何荣幸, 申伟, 李明   

  1. 西南大学化学化工学院 重庆 400715
  • 收稿日期:2012-09-07 出版日期:2012-11-28 发布日期:2012-10-17
  • 通讯作者: 申伟, 李明 E-mail:shenw@swu.edu.cn, liming@swu.edu.cn
  • 基金资助:
    项目受国家自然科学基金(No. 21073144)、重庆市自然科学基金(No. CSTC, 2009BB4104)、中央高校基本科研业务费(No. XDJK2010B009)资助.

Theory Design of Two Polymer Donors for Organic Heterojunction Solar Cells

Liu Xiaorui, Chen Chunxiang, He Rongxin, Shen Wei, Li Ming   

  1. School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715
  • Received:2012-09-07 Online:2012-11-28 Published:2012-10-17
  • Supported by:
    Project supported by the National Natural Science Foundation of China (No. 21073144), the Natural Science Foundation Project of CQ CSTC (No. CSTC, 2009BB4104), and the Fundamental Research Funds for the Central Universities (No. XDJK2010B009).

模拟了以苯并噻吩作为富电子基团分别与1H-benzo[d][1,2,3]triazole和1H-benzo[d][1,2,3]triazole-6-carbonitrile作为缺电子基团构成的两种聚合物太阳能电池供体材料(PBnDT-HTAZ, PBnDT-6CNTAZ)及PC60BM为受体材料的理论性质. 利用DFT理论分析了两种聚合物的电子和光物理性质, 通过Marcus理论研究了供-受体化合物在供受体界面的电荷转移性质和供体聚合物的空穴迁移能力. 计算结果表明: 供体聚合物具有强而宽的吸收, 并且具有强的分子内电子转移和从电子供体到电子受体的分子间电子转移, 对应的复合物都具有较小的激子束缚能; 与PBnDT-HTAZ相比, 设计的供体PBnDT-6CNTAZ, 由于引入了强吸电性的氰基而具有更大的开路电压和更好的抗氧化能力, 另外, 在供受体界面具有更好的电荷转移特性, 并且在供体中具有相对大的空穴迁移速率. 因此, 可以推断得知引入氰基的PBnDT-6CNTAZ是一种潜在的更好的太阳能电池供体材料.

关键词: 聚合物太阳能电池, 供-受体化合物, 苯并三唑, 电子转移

A highly efficient organic solar cell needs a copolymer as donor possessing low-band gap, high open-circuit voltage (Voc), good charge transfer at donor-acceptor (D-A) interface, and good transport properties in polymers. As the first step towards this goal, we constructed two polymers (PBnDT-HTAZ and PBnDT-6CNTAZ) incorporating benzodithiophene (BnDT) as the electron-rich units and either 1H-benzo[d][1,2,3]triazole (HTAZ) or 1H-benzo[d][1,2,3]triazole-6-carbonitrile (6CNTAZ) as the electron-deficient unit. The designed PBnDT-6CNTAZ was introduced a cyano in the electron-deficient unit. PBnDT-HTAZ and PBnDT-6CNTAZ as donors and [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) as an acceptor in hetero-organic solar cell, as well as the D-A complexes are investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) in this work. The electronic properties, optical absorption properties, intramolecular and intermolecular charge transfer, exciton binding energy of two polymers and corresponding D-A complexes are discussed. By means of Marcus theory, the exciton-dissociation, charge-recombination rate of D-A complex at the D-A interface, and the hole-transport rate of polymer donors are studied. According to the computational results, it indicates that the two polymers have strong and wide absorption peaks in visible region, as well as strong intramolecular charge transfer and intermolecular charge transfer for corresponding D-A complex. The designed PBnDT-6CNTAZ possesses lower the energy of the highest occupied molecular orbital (HOMO) so that PBnDT-6CNTAZ exhibits larger open-circuit voltage and better ability of antioxidant in comparison with PBnDT-HTAZ. The two polymers corresponding D-A complexes have small exciton binding energy. The PBnDT-6CNTAZ has good ability of charge transfer and larger hole-transport rate in comparison to PBnDT-HTAZ. It is thus clear that incorporating cyano in polymer (PBnDT-6CNTAZ) have an important impact on performance of organic solar cell. Therefore, we can infer that PBnDT-6CNTAZ may be a potential donor material of bulk heterojunction solar cells. The present calculated results demonstrated a first attempt of providing a theoretical model for the introduction of electron-deficient groups in copolymer donors. These results may provide a structural guideline for optimizing chemical construction of copolymer donors to improve the performance of bulk heterojunction solar cells. Our computational models and conclusions can be applied to design and predict other new polymer donors.

Key words: organic solar cell, donor-acceptor complex, benzotriazole, charge transfer