A trap-assisted ultrasensitive near-infrared organic photomultiple photodetector based on Y-type titanylphthalocyanine nanoparticles

Based on Y-type titanylphthalocyanine nanoparticles (Y-TiOPc NPs) with an average diameter of 2.5 +/- 0.6 nm, a trap-assisted ultrasensitive near-infrared organic photodetector (NIR OPD) has been successfully fabricated using the dip-coating process. The prepared OPD exhibited an obvious photomultiplication phenomenon with the highest external quantum efficiency (EQE) of 354 200%, an excellent photosensitivity with the maximum photoresponsivity (R) of 2227 A W-1, and an outstanding low-light detection with the highest normalized detectivity (D*) of 3.1 x 10(14) Jones under 780 nm illumination with a low intensity of 0.1 mu W cm(-2) at + 15 V mu m(-1). Such performances were attributed to the ultrasmall Y-YiOPc NPs with remarkable photosensitivity and a high surface-to-volume ratio which can enhance external hole tunneling injection assisted by trapped-electrons at the photoactive layer/ITO interface. The high EQE and R properties of the device, as well as the prompt, steady and reproducible photocurrent response during repeated on/off cycles of illumination, suggested that the prepared OPD was desired for ultrasensitive NIR detection. Therefore, the ultrasmall Y-TiOPc NPs proposed in this study showed great promising application in the large-area and low-cost solution process of ultrasensitive NIR OPDs.