Ultrasensitive organic phototransistors with multispectral response based on thin-film/single-crystal bilayer structures

We report on highly efficient organic phototransistors (OPTs) based on thin-film/single-crystal planar bilayer junctions between 5,6,11,12-tetraphenyltetracene (rubrene) and [ 6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM). The OPTs show good field-effect characteristics in the dark, with high hole-mobility (4-5cm(2) V-1 s(-1)), low-contact resistance (20 k Omega cm), and low-operating voltage (<= 5V). Excellent sensing capabilities allow for light detection in the 400-750 nm range, with photocurrent/dark current ratio as high as 4 x 10(4), responsivity on the order of 20AW(-1) at 27 mu Wcm(-2), and an external quantum efficiency of 52 000%. Photocurrent generation is attributed to enhanced electron and hole transfer at the interface between rubrene and PC61BM, and fast response times are observed as a consequence of the high-mobility of the interfaces. The optoelectronic properties exhibited in these OPTs outperform those typically provided by a-Si based devices, enabling future applications where multifunctionality in a single-device is sought. (C) 2015 AIP Publishing LLC.