Carrier Injection Mechanisms in Diketopyrrolopyrrole Organic Semiconductors

Organic semiconductors based on diketopyrrolopyrrole (DPP) are a new class of small molecule semiconductors which are air-stable, possess relatively high mobilities, and have been recently shown to undergo excitonic singlet fission. Realizing high quality (Ohmic) contacts to DPP is essential for the fabrication of high quality devices. In this work we use a combination of scanning Kelvin probe microscopy and electrical transport measurements to spatially map the work function in several DPP-based semiconductors and study the carrier injection mechanism in thermally evaporated DPP films.