Negative capacitance in polymer-nanocrystal composites

Abstract

The effect of negative capacitance (NC) was observed and investigated in conducting polymers with embedded PbS nanocrystals. NC occurred for signal frequencies up to 1MHz and was absent in control samples without nanocrystals. The amplitude of NC increased with the applied bias and was accompanied by a superlinear current–voltage characteristic. A theoretical description of NC is presented based on a voltage-induced redistribution of carriers in a nonuniform sample with nanocrystals playing the role of potential wells for carriers. The characteristic time of carrier capture by nanocrystals, determined from the frequency dispersion of NC, was ∼3×10−5s.