Excited state dynamics and exciton diffusion in triphenylamine/dicyanovinyl push–pull small molecule for organic optoelectronics

Abstract

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.

Highly electrochemically and thermally stable donor–π–acceptor triphenylamine-based hole-transporting homopolymersviaoxidative polymerization

“…Synthesis of TA-TDCV-PF has been described previously. 64 Preparation of the monomer TA-TDCV-H consists of three steps (Fig. 2(a)).…”

“…Synthesis of TA-TDCV-PF has been described previously. 64 Preparation of the monomer TA-TDCV-H consists of three steps (Fig. 2 The oxidative coupling polymerization of monomers TA-TDCV-H and TA-TDCV-PF was carried out at room temperature in nitrobenzene solution using FeCl 3 as an oxidant and the method adapted from ref.…”

Self-Assembly-Directed Exciton Diffusion in Solution-Processable Metalloporphyrin Thin Films

“…Monte Carlo diffusion computational simulation was used to determine exciton diffusion coefficient and diffusion lengths in the metalloporphyrin thin films [ 31 ]. This simulation method has been used previously for similar molecules, conjugated polymers, and organic dyes [ 32 , 33 , 34 , 35 , 36 ]. To study steady-state quenching in thin films, C 60 was doped in the metalloporphyrin solution in volume fraction 0.06% and 0.2% [ 37 ].…”

Diffusion-enhanced exciton dissociation in single-material organic solar cells

“…The probability of exciton dissociation at a domain boundary can be obtained more accurately from KMC simulations [36][37][38][39] by fitting the KMC simulated transients to the experimental PL transients. First, we obtained parameters of exciton diffusion into different directions, i.e.…”