This work presents a thin film device, combining, on the same glass substrate, photosensors and long-pass interferential filter to achieve a compact and efficient sensor for biomolecule detection. The photosensors are amorphous silicon stacked structures, while the interferential filter is fabricated alternating layers of silicon dioxide and titanium dioxide, directly grown over the photosensors. The system has been optimized to effectively detect the natural fluorescence of Ochratoxin A, a highly toxic mycotoxin present in different food commodities. In particular, the long-pass interferential filter has been designed to reject the wavelengths arising from the excitation source (centered at 330 nm) thus transmitting the OTA emission spectrum (centered at 470 nm). Experimental results show that the filter strongly reduces the photosensors quantum efficiency below 420 nm, while keeps it nearly constant at higher wavelength. © Springer International Publishing AG 2018.