Charge-Transfer states for high-performance organic electronics
Thin films comprising a blend of electron donating (D) and electron accepting (A) molecules are ubiquitous in organic electronic devices. At the D-A interfaces, intermolecular charge-transfer (CT) states form, in which an electron is transferred from D to A. Electrical doping (p- and n-type) involves ground-state CT from dopant to host and results in increased conductivities of the host organic semiconductor. Furthermore, the performances of organic solar cells, photodetectors and light emitting diodes depend crucially on  D-A interfaces where the CT state is an excited state, mediating between photons and free charge carriers. New applications of intermolecular CT states, such as transparent conductors, artificial synapses, biosensors, organic persistent luminescent materials and low cost narrowband near-infrared sensors have emerged in the past years, and there is clearly potential for additional innovation. However, current progress is hampered by a lack of understanding of the fundamental properties of intermolecular CT states and their decay and dissociation mechanisms. ConTROL aims to fill this knowledge gap and link device performance to molecular parameters of D-A interfaces. Electro-optical properties will be tuned by molecular design and appropriate D-A selection, as well as by weak and strong interactions with the opto-electronic device’s optical cavity. The knowledge generated will not merely result in improved performance of existing organic electronic devices, but new avenues and novel exciting applications of intermolecular CT states will be demonstrated.