Performance Enhancement of FET-Based Photodetector by Blending P3HT With PMMA

In this letter, we presented a solution-processed photodetector with a configuration of field-effect transistor (FET) ITO/poly(4-vinylphenol) (PVP)/poly(3-hexylthiophene) (P3HT): poly(methyl methacrylate) (PMMA)/Au in which PVP acts as a dielectric layer and different PMMA content (20 wt.% ∼60 wt.%) in P3HT as active layer. The best electrical property of the photodetector under no illumination was obtained with 20 wt.% PMMA content and the maximum ON-OFF current ratio and hole mobility of the as-prepared devices are 329 and 1.6 × 10^-3 cm²/V·s, respectively. Under illumination with wavelengths varying from 350 to 650 nm, however, the 50 wt.% PMMA content device demonstrated highest performance, showing a maximum photoresponsivity of 166.45 mA/W under 65∼μW/cm² of 600-nm illumination. Atom force microscope (AFM) phase images of P3HT:PMMA film certify the phase separation between P3HT and PMMA, as well as the crystallinity improvement of P3HT film after blending PMMA. The performance of FET-based photodetector under illumination is discussed.