Self-powered TiO2 NRs UV photodetectors: Heterojunction with PTTh and enhanced responsivity by Au nanoparticles

In this paper, novel self-powered p-n heterojunction UV photodetectors (TiO2 nanorod arrays/polyterthiophene (TiO2 NRs/PTTh) and TiO2 nanorod arrays/Au nanoparticles/polyterthiophene (TiO2 NRs/Au/PTTh)) are successfully constructed by combining the hydrothermal method and electrochemical deposition method. The structures, morphologies and photocurrent response properties of TiO2 NRs/PTTh and TiO2 NRs/Au/PTTh heterojunction UV photodetectors are systematically studied. These results show that TiO2 NRs/PTTh UV photodetector has self-powered performance, and also exhibit high sensitivity, good stability and fast response. Furthermore, the detection performance of UV photodetector could be further improved by using Au NPs as the middle layer due to the pyro-phototronic effect between Au NPs and TiO2 NRs. The responsivity (R) of TiO2 NRs/PTTh and TiO2 NRs/Au/PTTh UV photodetectors are respectively 0.0774 mA/W and 1.894 mA/W, and the detectability (D*) are respectively 2.155 × 109 Jones and 1.666 × 1010 Jones. Compared with the TiO2 NRs/PTTh UV photodetector, the rise time (τr) and fall time (τf) of TiO2 NRs/Au/PTTh UV photodetector are obviously shortened. And these results also confirm that the TiO2 NRs/Au/PTTh UV photodetector with heterojunction structure is a suitable candidate for self-powered UV photodetector. This work offers an effective strategy for the development of self-powered UV photodetectors. [Display omitted] •A self-powered UV photodetector was fabricated on based on FTO/TiO2 NRs/Au/PTTh/FTO structure.•A responsivity up to 1.89 mA/W was achieved without any external voltage.•The novel p-n heterojunction shall be applicable for UV detection.•The good response speed benefits from the pyro-phototronic effect and the built-in field.