The influence of an ultrathin 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) fluorescent dye layer at donor/acceptor heterojunction on the performance of small-molecule organic photovoltaic (OPV) cell is studied.The structure of OPV cell is of indium-tin oxide (ITO)/copper phthalocyanine (CuPc)/DCJTB/fullerene (C 60)/bathophenanthroline (Bphen)/Ag.The results show that open circuit voltage (V OC) increases to 0.57 V as the film thickness of DCJTB layer increases from 0.2 to 2.0 nm.By using an equivalent circuit model,the enhancement of V OC is found to be attributed to the reduced reverse saturation current density (J S) which is due to the lower highest occupied molecular orbital (HOMO) level in DCJTB than that in CuPc.Also,the short circuit current density (J SC) is affected when the DCJTB layer becomes thicker,resulting from the high series resistance R S A due to the low charge carrier mobility of fluorescent red dye.
High-performance phosphorescent white organic light-emitting devices (PhWOLEDs) with color stability and low efficiency decay are demonstrated by inserting wide band-gap materials between emitting layers. The two devices with N,N'- dicarbazolyl-3,5-benzene (mCP) and p-bis(triphenylsilyl)benzene (UGH2) as the interlayer exhibit both slight Commission Internationale del'Eclairage (CIE) coordinates variations of (±0.010, ±0.005) and (±0.013, ±0.006) in a wide voltage range, and low decay in current efficiency which shifts from the peak value 35.4 cd·A-1 and 27.4 cd·A-1 to 28.8 cd·A-1 and 23.5 cd·A-1 at 40000 cd·m-2 , respectively. The improvements are attributed to the charge carriers balance and the elimination of energy transfer loss by confining the carrier accumulation at the exciton formation interface through the interlayer.
C_(60)field-effect transistor (OFET) with a mobility as high as 5.17 cm 2 /V·s is fabricated.In our experiment,an ultrathin pentacene passivation layer on poly-(methyl methacrylate) (PMMA) insulator and a bathophenanthroline (Bphen)/Ag bilayer electrode are prepared.The OFET shows a significant enhancement of electron mobility compared with the corresponding device with a single PMMA insultor and an Ag electrode.By analysing the C_(60) film with atomic force microscopy and X-ray diffraction techniques,it is shown that the pentacene passivation layer can contribute to C_(60) film growth with the large grain size and significantly improve crystallinity.Moreover,the Bphen buffer layer can reduce the electron contact barrier from Ag electrodes to C_(60) film efficiently.
The performance of an organic photovoltaic(OPV) cell based on copper phthalocyanine CuPc/C60 with a tris(8-hydroxyquinolinato) aluminum(Alq3) buffer layer has been investigated.It was found that the power conversion efficiency of the device was 1.51% under illumination with an intensity of 100 mW/cm2,which was limited by a squareroot dependence of the photocurrent on voltage.The photocurrent-optical power density characteristics showed that the OPV cell had a significant space-charge limited photocurrent with a varied saturation voltage and a three quarters power dependence on optical power density.Also,the absorption spectrum was measured by a spectrophotometer,and the results showed that the additional Alq3 layer has a minor effect on photocurrent generation.
