Improvement of efficiency of polymer solar cell by incorporation of the planar shaped monomer in low band gap polymer

• Published in: Synthetic metals 2012-06, Vol.162 (9-10), p.768-774
• Main Authors: Shin, Woong, Jo, Mi Young, You, Dae Sung, Jeong, Yeon Sook, Yoon, Do Y., Kang, Jae-Wook, Cho, Jeong Ho, Lee, Gun Dae, Hong, Seong-Soo, Kim, Joo Hyun
• Format: Article
• Language: English
• Subjects: Aluminum; Applied sciences; Backbone; Blends; Devices; Electronics; Energy; Exact sciences and technology; Field effect mobility; Indium tin oxide; Morphology; Natural energy; Organic polymers; Photovoltaic cells; Photovoltaic conversion; Physicochemistry of polymers; Polymer solar cell; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Roughness; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Suzuki coupling; Transistors
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2012.02.004

[Display omitted] ► We introduce planar and rigid shaped monomer in the polymer back bone. ► The polymer with rigid and planar shaped monomer has higher field effect mobility. ► The blend of the polymer and PCBM shows well-penetrated morphology. ► The PCE of the polymer are better than the polymer without planar shaped monomer. A new π-conjugated polymer (PFDTBT-BTBT) with planar core based on 4,7-dithiophen-2-yl-benzo(2,1,3)thiadiazole (BT), [1]benzothieno-[3,2-b][1]benzothiophene (BTBT) and 9,9-didecylfluorene was synthesized by the Suzuki coupling reaction. In order to improve the photovoltaic performance, we introduce planar and rigid shaped BTBT in the polymer backbone. We also synthesized alternating copolymer of 9,9-didecylfluorene and BT (PFDTBT) to compare with optical, electrochemical and photovoltaic properties. The HOMO and LUMO energy levels of PFDTBT-BTBT were −5.67 and −3.75eV, respectively, which were very similar to those of PFDTBT (−5.65 and −3.75eV). The power conversion efficiency (PCE) of the device with a structure of ITO/PEDOT:PSS/PFDTBT-BTBT:PCBM (1:3)/Al was 2.08%, which is higher than that of PFDTBT:PCBM (1:3) (1.66%). The root-mean-square (RMS) roughness of PFDTBT-BTBT:PCBM (1:3) blend was 0.820nm, which was smaller than that of PFDTBT:PCBM (1:3) blend (1.75nm). PFDTBT-BTBT:PCBM showed smaller domain size and more well-penetrated morphology than PFDTBT:PCBM. The average field-effect hole mobility of the PFDTBT-BTBT was 6.2×10−4cm2/Vs, much larger than that of PFDTBT (2.3×10−4cm2/Vs). The results strongly support that polymer solar cell based on PFDTBT-BTBT shows better performance than that of the device based on PFDTBT.