Abstract
Optical activation of material properties illustrates the potentials held by tuning light-matter interactions with impacts ranging from basic science to technological applications. Here, we demonstrate for the first time that composite nanostructures providing nonlocal environments can be engineered to optically trigger photoinduced charge-transfer-dynamic modulations in the solid state. The nanostructures explored herein lead to out-of-phase behavior between charge separation and recombination dynamics, along with linear charge-transfer-dynamic variations with the optical-field intensity. Using transient absorption spectroscopy, up to 270% increase in charge separation rate is obtained in organic semiconductor thin films. We provide evidence that composite nanostructures allow for surface photovoltages to be created, which kinetics vary with the composite architecture and last beyond optical pulse temporal characteristics. Furthermore, by generalizing Marcus theory framework, we explain why charge-transfer-dynamic modulations can only be unveiled when optic-field effects are enhanced by nonlocal image-dipole interactions. Our demonstration, that composite nanostructures can be designed to take advantage of optical fields for tuneable charge-transfer-dynamic remote actuators, opens the path for their use in practical applications ranging from photochemistry to optoelectronics.
Highlights
Optical activation of material properties illustrates the potentials held by tuning light-matter interactions with impacts ranging from basic science to technological applications
The composite nanostructures are made of 4 pairs (4p) of 10-nmthick silver (Ag) and aluminum oxide (Al2O3) successive layers, with the last Al2O3 top-cover ranging from 10 nm to 1 μm
The donor:acceptor molecule is made of triphenylene and perylene diimide moieties chemically grafted with a flexible decyloxy bridge leading to a dyad, which can be spin-coated on top of the composite nanostructures[41,53]
Summary
They could become an attractive tool to qualitatively model the charge-transfer-dynamic modulations reported, even though at the likely identifying a bridge between intensity and kinetics. Long lasting surface photovoltages contribute to optical effects which are supported by the composite nanostructures and combine to image-dipole interactions on charge-transfer states to form nonlocal enhanced optical field (NEOF) resulting in the chargetransfer-dynamic modulations. These should naturally be described in the framework of Marcus theory, as presented . Assuming that the donor excited and ground states do not carry any dipole moment, that VAD is independent of the optical field, and considering that ÀΔ~μ:~F is a perturbation, Taylor series expansion to the 2nd order leads to the following expression: kNCTEOF % kICDTI:À1 þ δF1F þ δF2F2Á ð5aÞ τ
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