Organic phototransistors based on perylene diimide nanocrystals lacking pi-pi interactions

We report on the fabrication and characterization of organic phototransistors (OPTs) based on fluorescent nanocrystals assembLed from a simple organic dye molecule (N,N' -bis(2,4-dimethylpent-3-yl)perylene-3,4:9,10-tetracarboxylic diimide, DMP-PDI). The OPT active Layer is based on DMP-PDI nanocrystals assembLed in aqueous solution or within polymer films. Despite the absence of any pi-overlap, the nanocrystals show mobilities as high as (5 +/- 1) x 10(-3) cm(2) V-1 s(-1) in polymer films, which is due to imide/ pi-core noncovalent interactions Leading to substantial electronic coupling as revealed by computational studies. The OPTs strongly respond to white Light irradiation, resulting in a decrease in threshoLd voltage by as much as 40 V. OPTs based on nanocrystals assembLed within poLymer fiLms have threshoLd voltages dose to 0 V upon illumination and a high photo/dark current ratio (P = 4 x 10(3)). We show that the organic crystals Lacking pi-overlap mediate charge mobility and are advantageous as active Layers for OPTs due to diminished nonradiative decay.