In Situ Monitoring of Polaron Localization and Cell Activity with Charge Accumulation Spectroscopy

Localization of charge carriers directly affects charge transport and local potential fluctuations and is a critical factor dictating the performance of organic bioelectronic devices. Understanding how the polaron localization at the solid-water interface is influenced by the microscopic structural ordering of the organic semiconducting films can provide complementary information to achieve better control on the electrochemical stability of bioelectronic devices. Here, charge accumulation spectroscopy is utilized to explore the structure-dependent polaron localization in an electrolyte-gated organic field-effect transistor structure. The results reveal that the ordered and closely packed systems exhibit much higher absorption cross-sections (sigma(p)) than disordered and isolated molecules. Therefore, the charge-induced absorption feature can be utilized to monitor in situ the microscopic morphology variations of organic semiconducting films under electrolyte and trace the entire cell detachment process noninvasively. This study suggests that the spectroscopic signature of polaronic charge carriers, which is highly sensitive to the local environment surrounding the probed chromophores, serves as an effective probe to detect the structure-dependent charge transport features in organic bioelectronic devices.