WFU Physics Colloquium

Organic semiconductors and hybrid organic/inorganic perovskite semiconductors can address new applications, which are off-limits for conventional silicon-based electronics. We fabricate organic field-effect transistors (OFETs) and through the use of several device architectures, in combination with surface treatments, we were able to achieve mobilities as high as 6.8 cm2/Vs. We find that the microstrain induced in the organic semiconductor layer by the mismatch in the thermal expansion between the consecutive device layers generates trapping states and localize charge carriers, leading to a surprising universal scaling between the activation energy of the devices and the interfacial thermal expansion mismatch coefficient. The second class of materials of interest to this study is that of hybrid perovskite methylammonium lead halides. When we developed the first working field-effect transistor on these materials, we were able to measure the nature and dynamics of charge carriers directly. We found balanced ambipolar transport with mobilities of 1 cm2/Vs for both electrons and holes.