Spectroscopic Assessment of Charge-Carrier Mobility in Crystalline Organic Semiconductors

Further progress in organic electronics demands new highly efficient organic semiconductor (OS) materials. So far, however, band-like charge transport with high mobilities has been reliably demonstrated only in a few OSs, and development of efficient methods for search of high-mobility materials among a plethora of OSs remains extremely important. In the present work, a spectroscopic method is presented for screening of crystalline OSs with efficient charge transport, to be used prior to time-consuming device measurements. Specifically, the work focuses on a physical rationale and an experimental benchmark of a correlation between the intensities of the low-frequency Raman spectrum and the strength of dynamic disorder limiting the charge-carrier mobility in a material. As a result, two physics-inspired spectroscopic descriptors for charge-carrier mobility estimation are suggested, both of which clearly correlate with device mobilities reported for various crystalline OSs. It is anticipated that the spectroscopic method based on these descriptors can serve as a powerful search tool for revealing new high-mobility OS materials.