Raul Benedito A L, Luponosov Yuriy N, Yang Wenyan, Surin Nikolay M, Douhéret Olivier, Min Jie, Jansen Thomas L C, Ponomarenko Sergei A, Pshenichnikov Maxim S
Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands.
Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya 70, Moscow, 117393, Russia.
Sci Rep. 2020 Dec 3;10(1):21198. doi: 10.1038/s41598-020-78197-2.
Triphenylamine-based small push-pull molecules have recently attracted substantial research attention due to their unique optoelectronic properties. Here, we investigate the excited state de-excitation dynamics and exciton diffusion in TPA-T-DCV-Ph-F small molecule, having simple chemical structure with asymmetrical architecture and end-capped with electron-withdrawing p-fluorodicyanovinyl group. The excited state lifetime in diluted solutions (0.04 ns in toluene and 0.4 ns in chloroform) are found to be surprisingly shorter compared to the solid state (3 ns in PMMA matrix). Time-dependent density functional theory indicates that this behavior originates from non-radiative relaxation of the excited state through a conical intersection between the ground and singlet excited state potential energy surfaces. Exciton diffusion length of ~ 16 nm in solution processed films was retrieved by employing time-resolved photoluminescence volume quenching measurements with Monte Carlo simulations. As means of investigating the device performance of TPA-T-DCV-Ph-F, we manufactured solution and vacuum processed bulk heterojunction solar cells that yielded efficiencies of ~ 1.5% and ~ 3.7%, respectively. Our findings demonstrate that the short lifetime in solutions does not hinder per se long exciton diffusion length in films thereby granting applications of TPA-T-DCV-Ph-F and similar push-pull molecules in vacuum and solution processable devices.
基于三苯胺的小推挽分子由于其独特的光电特性，最近引起了大量的研究关注。在此，我们研究了TPA-T-DCV-Ph-F小分子中的激发态去激发动力学和激子扩散，该小分子具有简单的化学结构，呈不对称结构，末端带有吸电子的对氟二氰基乙烯基。与固态（在PMMA基质中为3 ns）相比，稀释溶液中的激发态寿命（在甲苯中为0.04 ns，在氯仿中为0.4 ns）出人意料地短。含时密度泛函理论表明，这种行为源于激发态通过基态和单重激发态势能面之间的锥形交叉进行的非辐射弛豫。通过采用时间分辨光致发光体积猝灭测量和蒙特卡罗模拟，得出溶液处理薄膜中的激子扩散长度约为16 nm。作为研究TPA-T-DCV-Ph-F器件性能的手段，我们制造了溶液处理和真空处理的本体异质结太阳能电池，其效率分别约为1.5%和3.7%。我们的研究结果表明，溶液中的短寿命本身并不妨碍薄膜中激子的长扩散长度，从而使TPA-T-DCV-Ph-F和类似的推挽分子可应用于真空和溶液可加工器件。
