High performance self-powered ultraviolet photodetectors based on P(TTh-co-EDOT) copolymer sensitized TiO2 NRs

Abstract

A self-powered ultraviolet photodetector (UV PD) effectively utilizes UV energy and has attracted greatly attention due to its no consuming of any external power. In this work, TiO2 nanoarrays (NRs) were synthesized by a one-step hydrothermal method, which was combined with P(TTh-co-EDOT) to realize a high-performance p-n heterojunction UV PD, and P(TTh-co-EDOT) was evaluated as the photosensitive layers in UV PDs for the first time. Furthermore, the working mechanism for the self-powered of UV PD was discussed in detail based on the energy band theory. Different electrochemical deposition cycles of TTh-co-EDOT on the surface of TiO2 NRs were applied to form p-n heterojunction for achieving the optimum photoelectric performance. Among them, it was found that the optimum UV PD based on face-to-face fabrication of TiO2 NRs and P(TTh-co-EDOT) from 3 deposition cycles exhibits an enhancement of photoelectric performance without applying any external voltage. Benefiting from the enhanced built-in electric field of the TiO2 NRs/P(TTh-co-EDOT) interface, balancing photogenerated carriers and the charge separation and transport in self-power mode, the responsivity and detectivity of TiO2 NRs/P(TTh-co-EDOT)-3C are 2.252 mA/W and 3.413 × 1010 Jones, with the rise and fall times are 0.256/0.427 s, which exhibited excellent photoelectric properties and stability. TiO2 NRs/P(TTh-co-EDOT)-1C has the lowest responsivity (0.0995 mA/W) and detectivity (6.035 × 109 Jones) and TiO2 NRs/P(TTh-co-EDOT)-4C has the longest rise and fall times (0.460/0.451 s). These results suggest that the great potential of the TiO2 NRs and P(TTh-co-EDOT) for high-performance UV PDs.