Innovative applications in light signal sensing require flexibility, lightweight, low-cost and low temperature processability, as well as high sensitivity and quantitative photoresponse. We report on flexible organic phototransistors (OPTs) with excellent reproducibility in the detection of outstandingly low light intensities of few nW cm−2. The optical response of the phototransistor was thoroughly characterized as a function of the wavelength, the incident optical intensity and the electrical polarizations. The photodetectors work reliably under bending and pulse cycling in different environmental conditions, at low polarizations down to the range 0.1–5 V. Based on these outcomes, arrays for broadband or multiple wavelength detection were implemented and successfully tested. The proposed device structure, derived from a layered p-p heterojunction, was developed to be easily implementable in each wavelength of interest …