Abstract
The highly sensitive ultra-violet (UV) photodiode was demonstrated on the organic-inorganic hybrid heterostructure of β-phase p-type polyfluorene (PFO)/n-type yttrium-doped zinc oxide nanorods (YZO-NRs). The device was fabricated through a simple fabrication technique of β-phase PFO coating onto YZO-NRs that had been directly grown on graphene by the hydrothermal synthesis method. Under UV illumination (λ = 365 nm), the device clearly showed excellent photoresponse characteristics (e.g., high quantum efficiency ~690%, high photodetectivity ~3.34 × 1012 cm·Hz1/2·W−1, and fast response time ~0.17 s). Furthermore, the ratio of the photo current-to-dark current exceeds 103 even under UV illumination with a small optical power density of 0.6 mW/cm2. We attribute such superb photoresponse characteristics to both Y incorporation into YZO-NRs and conformation of β-phase PFO. Namely, Y dopants could effectively reduce surface states at YZO-NRs, and β-phase PFO might increase the photocarrier conductivity in PFO. The results suggest that the β-phase p-PFO/n-YZO-NR hybrid heterostructure holds promise for high-performance UV photodetectors.
Highlights
For the last two decades, ZnO nanostructures have garnered substantial attention because of their prodigious potential for blue and ultra-violet (UV) optoelectronic devices [1,2,3,4,5,6]
We recently reported that Y-doping led to the reduction of oxygen-related defects in YZnO (YZO) [22,23]; the electrical conductivity and the excitonic emission properties could be improved by Y doping into YZO films [19,20] and n-type yttrium-doped zinc oxide nanorods (YZO-NRs) [21,22,23], respectively
The hybrid PDs were effectively fabricated by spin-coating of β-phase PFO onto YZO-NRs that had been directly grown on graphene by the hydrothermal synthesis method
Summary
For the last two decades, ZnO nanostructures have garnered substantial attention because of their prodigious potential for blue and ultra-violet (UV) optoelectronic devices [1,2,3,4,5,6]. Multi-level memory cells [36,37], high speed barristors [38], color-tunable light-emitting diodes [18,39], and color-dependent photodiodes [40] are typical examples of ZnO-based inorganic-organic hybrid electronic and optoelectronic devices. Since β-phase PFO has a higher charge-carrier mobility than other organic semiconductors [44], many researchers have been devoted to demonstrating highly efficient solid-state light-emitting devices using the inorganic-organic hybrid heterostructure of ZnO/PFO [45,46,47,48,49]. Aiming at demonstrating the high-performance UV PDs by using PFO and YZO-NRs, we have investigated the fabrication and the characterization of the β-phase p-type PFO/n-type YZO-NRs organic-inorganic hybrid heterojunction PDs. The hybrid PDs were effectively fabricated by spin-coating of β-phase PFO onto YZO-NRs that had been directly grown on graphene by the hydrothermal synthesis method. We report on experimental data obtained from systematic analyses of the material-to-device characteristics
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