Sensitive, fast, stable, and broadband polymer photodetector with introducing TiO2 nanocrystal trap states

In this work, we synthesized ligand-free anatase TiO 2 nanocrystals with clean surface and excellent electron extraction. By introducing the trap states between the TiO 2 nanocrystals and the photoactive layer of poly (3-hexylthiophene) (P3HT): (phenyl-C61-butyric-acid-methyl-ester) (PC 61 BM) bulk heterojunction (BHJ), a high performance solution-processed broadband OPD in the visible wavelength is realized and characterized. The OPD shows near spectrally flat response from 350 to 650 nm with high EQE (113%), high responsivity (0.5 A/W) and high detectivity (1.9 × 10 12 Jones) at −1 V. The device also exhibits a high −3 dB bandwidth of 902 kHz and a respectable response speed with a rise time and fall time of 34 μs and 26 μs, respectively. The photocurrent retention measurement at a bias voltage of −1 V implies that the device photoresponse is significantly stable. These OPD performance parameters are sufficient for use in the machine vision or imaging systems. With the help of the J-V curves and light assisted C-V measurements, the underlying working mechanism is proposed as well.