Alternating current characterization of nano-Pt(Ⅱ)octaethylporphyrin(PtOEP) thin film as a new organic semiconductor

Alternating current(AC) conductivity and dielectric properties of thermally evaporated Au/Pt OEP/Au thin films are investigated each as a function of temperature(303 K–473 K) and frequency(50 Hz–5 MHz).The frequency dependence of AC conductivity follows the Jonscher universal dynamic law.The AC-activation energies are determined at different frequencies.It is found that the correlated barrier hopping(CBH) model is the dominant conduction mechanism.The variation of the frequency exponent s with temperature is analyzed in terms of the CBH model.Coulombic barrier height Wm,hopping distance Rω,and the density of localized states N(EF) are valued at different frequencies.Dielectric constant ε_1(ω,T) and dielectric loss ε_2(ω,T) are discussed in terms of the dielectric polarization process.The dielectric modulus shows the non-Debye relaxation in the material.The extracted relaxation time by using the imaginary part of modulus(M')is found to follow the Arrhenius law.     

Dissolved oxygen concentration field measurement in micro-scale water flows using PtOEP/PS film sensor

A planar optode system based on an oxygen quenchable luminophore platinum (II) octaethyporphrin (PtOEP) bound with thin polystyrene (PS) film and UV light-emitting diodes (UV-LEDs) was developed to measure the dissolved oxygen (DO) concentration field in micro-scale water flows. An intensity-based method adopting a pixel-to-pixel in situ calibration technique was used to visualize DO concentration fields around an impinging micro-nozzle. The achievable spatial resolution of the acquired concentration map could be as high as 2.94 μm. A micro-round water jet having 100% of DO was obliquely impinged on to a PtOEP/PS film coated plate placed in a 0% of DO water container. Velocity fields were obtained by computational fluid dynamics (CFD) analysis and it is demonstrated that the high DO concentration region was coincided with the impingement area. The DO concentration gradient due to DO diffusion was affected by the Reynolds number.     

Novel near-infrared photoluminescence from platinum(II)-porphyrin (PtOEP) aggregates

We investigated photoluminescence of the phosphorescent molecule platinum(II)-2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin. In neat films prepared by organic molecular beam deposition or precipitation from solution, we observe a near infrared emission feature around 1.65 eV, caused by aggregation effects.     

Organic LED device based on PtOEP phosphor without doping in host material

Electroluminescence (EL) and photoluminescence (PL) have been studied on multi-layer organic light-emitting diode (OLED) devices based on phosphorescent platinum octaethyl porphine (PtOEP) molecule. A multi-layer OLED (called Pt5) which has 100% PtOEP without doping in host as the emitting layer is investigated and compared its EL and PL characteristics with those of the other OLEDs (Pt2 and Pt3) with emitting layer of PtOEP doped in 4,4′-N,N′-dicarbazole-biphenyl (CBP) host material. It is observed that Pt5 shows a lower EL efficiency than Pt2 and Pt3. Three broad EL bands are observed at 500, 527 and 570 nm in the multi-layer device in addition to red sharp EL band due to PtOEP in Pt5, while only the red PtOEP EL is observed in Pt2 and Pt3. The 500, 527 and 570 nm EL peaks arise from absorption of the broad 525 nm Alq₃ emission band by PtOEP layer. The emission from the Alq₃ electron-transport layer is caused by the carrier leakage from the hole-blocking BAlq layer. The intensity of red EL due to PtOEP is much weaker in Pt5 than in Pt2. Taking into account the result of PL, it is suggested that highly efficient energy transfer from CBP host to PtOEP guest occurs in Pt2 and Pt3, giving rise to higher PtOEP luminance, while concentration quenching occurs in PtOEP layer in Pt5.