Xiqing Zhang

High response organic deep ultraviolet photodetector with PEDOT:PSS anode

We have fabricated an organic deep ultraviolet photodetector (PD) using PEDOT:PSS (PH 1000) as a transparent anode. NPB and PBD were employed as electron donor and acceptor, respectively. The PD exhibits a dark current of 0.0829 μA/cm(2) and a photocurrent of 85.3 μA/cm(2) at -12 V under 280 nm light illumination with an intensity of 0.488 mW/cm(2). A high response at 248-370 nm with its peak of 0.18 A/W at 280 nm and a detectivity of 1.1×10(12) cm Hz(1/2) u2009W(-1) were achieved. The more detailed mechanism of harvesting high performance and the dependence of photocurrent density on illumination intensity are also discussed.

Solar-Blind Photoresistors Based on

Solar-blind photoresistors based on Mg_0.48Zn_0.52O thin films were fabricated on r-plane sapphire substrates by radio-frequency plasma-assisted molecular beam epitaxy. High-quality a-plane-orientation single-phase wurtzite Mg_0.48Zn_0.52O thin films are demonstrated by X-ray diffraction and absorption spectra. The MgZnO photoresistors exhibit a large dark/photoresistance ratio up to 1.7 × 10⁴ with the light intensity of 0.61 mW/cm² at 260 nm. The spectral response shows a sharp response peak only in the solar-blind region with maximum responsivity of 1.5 × 10^-3 Ω^-1· W^-1.

\hbox{Mg}_{0.48} \hbox{Zn}_{0.52}\hbox{O}

An organic deep ultraviolet (DUV) photodetector (PD) with a response peak at 270 nm was fabricated. NPB and BAlq were employed as electron donor and acceptor, respectively, and polymer PEDOT:PSS was used as the transparent anode. The peak response of 0.14 A/W under illumination of 270-nm light with an intensity of 1.35 mW/cm² and a detectivity of 8.26×10¹¹ cmHz^1/2W^-1 at -12 V were achieved, and the corresponding quantum efficiency η reaches 64.3%. The PDs exhibit a low dark current of 8.97×10^-8 A/cm², and the photo-to-dark current ratio is about 2.1×10³ at -12 V. The realization of DUV detection is attributed to the strong absorption of shorter UV wavelengths of acceptor BAlq and high transmittance of PEDOT:PSS anode in DUV region. The mechanism of harvesting high performance is also discussed in detail.

Thin Films Grown on

Structural and optical properties of ZnO epilayers grown on r -plane sapphire substrates by plasma-assisted molecular-beam epitaxy have been investigated using various techniques. A high-purity wurtzite structure and a smooth surface with an a-plane orientation were obtained. The resonant Raman scattering spectra show a typical multiphonon vibration characteristic from wurtzite ZnO. A good near band gap luminescence property is revealed in photoluminescence spectra.

r\hbox{-Al}_{2} \hbox{O}_{3}

Organic ultraviolet photodetectors (PDs) with a narrow-band spectral response are fabricated. TAPC and PBD were utilized as the electron donor and acceptor, respectively. Glass/indium tin oxide (ITO) was employed as the anode contact and the incident light window. The PDs reveal a narrow response width of 30 nm at 316-346 nm. A peak response of 0.12 A/W at 330 nm and a photo-to-dark ratio of about 1.1 ×102 under 330-nm light illumination with an intensity of 0.95 mW/cm2 were achieved. The realization of the narrow-band response should be ascribed to the steep absorption of organic materials at the long wavelength and the blocking role of glass/ITO contact at the short wavelength.