Ultrasensitive organic phototransistors with multispectral response based on thin-film/single-crystal bilayer structures
Applied Physics Letters
American Institute of Physics (AIP)
© 2015 AIP Publishing LLC This is the author accepted manuscript. The final version is available from AIP via the DOI in this record.
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-C61-butyric acid methyl ester (PC61BM). The OPTs show good field-effect characteristics in the dark, with high hole-mobility (4-5 cm2 V-1 s-1), low-contact resistance (20 kΩ cm), and low-operating voltage (≤5 V). Excellent sensing capabilities allow for light detection in the 400-750 nm range, with photocurrent/dark current ratio as high as 4 × 104, responsivity on the order of 20 AW-1 at 27 μW cm-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.
The authors acknowledge the financial support from Fundação para a Ciência e Tecnologia (FCT) through Contract Nos. SFRH/BPD/84820/2012, IF/01088/2014, and funding through the IN and CICECO Associated Laboratories. A.N. thanks EPSRC for grant EP/M001024/1. The authors thank A. Kholkin (CICECO) for characterizing the PCBM films.
Vol. 107, No. 2, Article no. 223301