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Investigation of Optical and Dielectric Constants of Benzobis(thiazole)- based Copolymer Films

[ Vol. 10 , Issue. 3 ]


Yue Su, Ailing Yang*, Wenzhe Zhang and Shuguang Wen*   Pages 350 - 355 ( 6 )


Introduction: Copolymer PBB-T with benzo[1,2-d:4,5-d']bis(thiazole) (BBT) as the accepting unit and benzodithiophene (BDT) as the donor unit is a promising candidate for highperformance non-fullerene polymer solar cells (PSCs). So far optical and dielectric constants of the PBB-T are not fully known.

Method: PBB-T was synthesized and thin films of PBB-T were prepared. By using the Kramers-Kronig relations and the transmission spectra of the PBB-T films, the optical and dielectric constants, including in absorption coefficient (α(λ)), extinction coefficient (κ(λ)), refractive index (n(λ)), dielectric constant (ε1(λ),ε2(λ)), band gap (Eg) and mobility of the PBB-T films were calculated and analyzed.

Result: At 500 nm, α, κ, n, ε1 and ε2 are 1.65×105 cm-1, 0.46, 1.8163, 3.0 and 1.65 respectively. Eg is 2.111 eV. The hole mobility of PBB-T are 2.41×10-5 cm2 V-1 s-1 and 1.71×10-4 cm2 V-1 s-1 for the as-cast film and for the solvent vapor annealed film respectively. The results show that these optical and dielectric constants of the PBB-T films are almost independent on the thicknesses of the films, indicating our results are reliable. The features of the optical and dielectric constants show the PBB-T films are very promising candidates for high-performance non-fullerene PSCs and potential cut-off filter only permitting red and near-infrared light passing.

Conclusion: These results are significant for designing optoelectronic devices related to the PBBT thin films.


Benzobis(thiazole)-based copolymer films, Kramers-Kronig relations, transmittance spectra, absorption coefficient, extinction coefficient, refractive index, dielectric constant, band gap, hole mobility.


Department of Physics, Ocean University of China, Qingdao, Department of Physics, Ocean University of China, Qingdao, Department of Physics, Ocean University of China, Qingdao, Qingdao Institute of Bioenergy & Bioprocess Technology, Chinese Academy of Sciences, Qingdao

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