Optical-field driven charge-transfer modulations near composite nanostructures

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. Controlling and modulating charge transfer dynamics in composite nanostructures, though promising for optoelectronic applications, remains a challenge. Here, the authors report optical control of charge separation and recombination processes in organic semiconductor-based composite nanostructures.