Ultrafast Intramolecular Dynamics in Novel Star-Shaped Molecules for Photovoltaic Applications

Luponosov

Solodukhin

et al. 2018

Organic Electronics

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Section: External Quantum Efficiency Measurementsmentioning

confidence: 85%

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

Luponosov

Solodukhin

et al. 2018

Organic Electronics

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“…In all scenarios, the CT PL decays in time whereas obviously the latter scenario is more favorable for OSC operation. To directly observe the charge-separation processes, we performed time-resolved PIA measurements, which allow tracking the charge-separation dynamics. ,− With the PIA experiments, the two scenarios can be easily distinguished: in the case of CT state recombination, a gradual decrease in the PIA signal is expected. ,, …”

Section: Resultsmentioning

confidence: 99%

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

Liu

Luponosov³

et al. 2017

J. Phys. Chem. C

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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.

Ultrafast Charge Generation Pathways in Photovoltaic Blends Based on Novel Star‐Shaped Conjugated Molecules

Advanced Energy Materials

Luponosov

Ponomarenko

et al. 2014

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The quest for new materials is one of the main factors propelling recent advances in organic photovoltaics. Star‐shaped small molecules (SSMs) have been proven promising candidates as perspective donor material due to the increase in numbers of excitation pathways caused by the degeneracy of the lowest unoccupied molecular orbital (LUMO) level. In order to unravel the pathways of the initial photon‐to‐charge conversion, the photovoltaic blends based on three different SSMs with a generic structure of N(phenylene‐nthiophene‐dicyanovinyl‐alkyl)3 (n = 1–3), and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) acceptor are investigated by ultrafast photoinduced absorption spectroscopy assisted by density functional theory calculations. It is shown that both electron transfer from SSMs to PC71BM and hole transfer from PC71BM to SSMs are equally significant for generation of long‐lived charges. In contrast, intramolecular (intra‐SSM) charge separation results in geminate recombination and therefore constitutes a loss channel. Overall, up to 60% of long‐lived separated charges are generated at the optimal PC71BM concentrations. The obtained results suggest that further improvement of the SSM‐based solar cells is feasible via optimization of blend morphology and by suppressing the intra‐SSM recombination channel.