Trap healing and ultra low-noise Hall effect at the surface of organic semiconductors

Fundamental studies of intrinsic charge transport properties of organic semiconductors are often hindered by charge traps associated with static disorder present even in optimized single-crystal devices. Here, we report a novel method of surface functionalization using an inert non-conjugated polymer, perfluoropolyether (PFPE), deposited at the surface of organic molecular crystals, that results in accumulation of mobile holes and ``trap healing'' effect at the crystal/PFPE interface [1]. As a consequence, a remarkable ultra low-noise, trap-free conduction regime characterized by intrinsic mobility and transport anisotropy emerges in organic single crystals, and Hall effect measurements with unprecedented signal-to-noise ratio are demonstrated. This general method to convert trap-dominated organic semiconductors to intrinsic systems may enable the determination of intrinsic transport parameters with high accuracy and make Hall effect measurements in molecular crystals ubiquitous.\\[4pt] [1] B. Lee, Y. Chen, D. Fu, H. T. Yi, K. Czelen, H. Najafov, V. Podzorov, ``Trap healing and ultra low-noise Hall effect at the surface of organic semiconductors,'' Nature Mater. DOI 10.1038NMAT3781 (2013).