Organic semiconductors (OSCs) constitute an attractive platform for optoelectronics design due to the ease of processing such materials and their inherent tunability through functionalization. Incorporating OSCs into electrical circuits requires forming junctions between them and other materials, yet the change in dielectric properties about these junctions can strongly perturb the electronic structure of the OSC. Specifically, the morphology of the interface between two materials greatly affects their ability to transfer charge and energy through the device. To study these processes, a technique is required that can characterize excited species at buried interfaces in working devices. To study these inaccessible interfaces in situ, we have adapted electronic sum frequency generation (ESFG). This technique is an interface specific spectroscopy that allows for measuring how both the electronic structure and film morphology affect energy transfer across interfaces in OSCs. However, as this technique is generated exclusively from junctions in a device the signal is inherently weak, being generated from only a few monolayers in the film. We have been able to improve our sensitivity to weak signals using heterodyne detected ESFG (HD-ESFG). HD-ESFG incorporates an additional signal from a strong, bulk allowed non-resonant source that significantly improves signal to noise and sensitivity to morphology for the ESFG from an interface. Additionally, we have incorporated the ability to tune our non-resonant upconversion beam to study a broader landscape of available energetic levels within a molecular interface. Our work demonstrates that HD-ESFG can be used to enhance the inherently weak signals of direct ESFG from the interfaces of OSC devices and the tuning of the generation beams used for ESFG can give greater information about the electronic structure of buried interfaces.<br/>

Measuring buried interfacial electronic structure using heterodyne detected electronic sum frequency generation

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.