Subnanosecond Charge Recombination Dynamics in P3HT/PC61BM Films

Molecules

Wei Zhang¹  Ning-Jiu Zhao¹  Ming-Ming Huo¹  Li-Min Fu¹  Xi-Cheng Ai¹ 

[1] ¹Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001, China ²Department of Chemistry, Renmin University of China, Beijing 100872, China

关键词: [6;    6]-phenyl-C₆₁-butyric acid methyl ester (PCBM);    poly(3-hexylthiophene) (P3HT);    solvent vapor annealing (SVA);    time-resolved spectroscopy;    bimolecular charge recombination;    trap states;   

DOI  :  10.3390/molecules171213923

来源: mdpi

【 摘 要 】

Ultrafast near-infrared absorption spectroscopy was used to investigate the influence of film morphology and excitation photon energy on the charge recombination (CR) dynamics in the initial nanosecond timescale in the P3HT/PC₆₁BM blend films. With reference to the CS₂-cast films, the solvent vapor annealed (SVA) ones show 2–3-fold improvement in hole mobility and more than 5-fold reduction in the polymer-localized trap states of holes. At Dt = 70 ps, the hole mobility (m_h) and the bimolecular CR rate (g_bi) of the SVA films are m_h = 8.7 × 10^{−4 cm2}×s⁻¹×V⁻¹ and g_bi = 4.5 × 10^{−10 cm3}×s⁻¹, whereas at Dt = 1 ns they drop to 8.7 × 10^{−5 cm2}×s⁻¹×V⁻¹ and 4.6 × 10^{−11 cm3}×s⁻¹, respectively. In addition, upon increasing the hole concentration, the hole mobility increases substantially faster under the above-gap photoexcitation than it does under the band-gap photoexcitation, irrespective of the film morphologies. The results point to the importance of utilizing the photogenerated free charges in the early timescales.

【 授权许可】

CC BY   
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.