Triphenylamine-Based Push–Pull Molecule for Photovoltaic Applications: From Synthesis to Ultrafast Device Photophysics

Abstract

Small push–pull molecules attract much attention as prospective donor materials for organic solar cells (OSCs). By chemical engineering, it is possible to combine a number of attractive properties such as broad absorption, efficient charge separation, and vacuum and solution processabilities in a single molecule. Here we report the synthesis and early time photophysics of such a molecule, TPA-2T-DCV-Me, based on the triphenylamine (TPA) donor core and dicyanovinyl (DCV) acceptor end group connected by a thiophene bridge. Using time-resolved photoinduced absorption and photoluminescence, we demonstrate that in blends with [70]PCBM the molecule works both as an electron donor and hole acceptor, thereby allowing for two independent channels of charge generation. The charge-generation process is followed by the recombination of interfacial charge transfer states that takes place on the subnanosecond time scale as revealed by time-resolved photoluminescence and nongeminate recombination as follows from the OSC performance. Our findings demonstrate the potential of TPA-DCV-based molecules as donor materials for both solution-processed and vacuum-deposited OSCs.

Simple donor-acceptor molecule with long exciton diffusion length for organic photovoltaics

“…Low VOC losses were also previously found in linear [70] and star-shaped [54] TPA-DCV-based molecules. Partially, the low VOC loss in TPA-T-DCV-Ph:C70 is explained by the low energy disorder [71] of TPA-T-DCV-Ph; however, the share of disorder-induced VOC losses to the total losses are typically only ~0.1 V [72].…”

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

“…The larger Stokes shift in chloroform as compared to toluene is ascribed to the higher polarity of the former that leads to increased energy relaxation to longer wavelengths 27,28 . The absorption and PL spectra maxima peak positions of the molecules dispersed in PMMA matrix are slightly shifted compared to the diluted solutions, which is also attributed to the difference in medium polarizability 10,15 . www.nature.com/scientificreports/ Figure 2b shows the PL transients of TPA-T-DCV-Ph-F in solutions and in PMMA matrix with the respective independently measured PL quantum yield (QY) values.…”

“…Despite the extensive research on TPA/DCV small molecules, there are just few experimental and theoretical works which investigate their excited state photophysical behavior 6,[10][11][12][13][14][15] . Specifically, studies geared towards understanding the ultrafast photo-induced processes in solution and the corresponding correlation to the solidstate have not been thoroughly addressed.…”

Solution‐Processable Unsymmetrical Triarylamines: Towards High Mobility and ON/OFF Ratio in Bottom‐Gated OFETs

“…Triarylamine( TAA)-based organic semiconductors are holetransporting, electron-donating materials and are used as components in different devices [15] owingt ot heir low reorganization energy.M olecules with linear and cyclic architectures constructed on the basis of TAAs are extensively employed in optoelectronic devices due to their good charget ransport and emissive nature. [16] The particular geometrical features of TAAs will shed light on the structure-property relationship.T hey have been studied as suitable materials for OFETsi nthe past two decades.…”