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The instability of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with different active layer thicknesses under temperature stress has been investigated through using the density-of-states (DOS). Interestingly, the a-IGZO TFT with 22 nm active layer thickness showed a better stability than the others, which was observed from the decrease of interfacial and semiconductor bulk trap densities. The DOS was calculated based on the experimentally-obtained activation energy ( E A ), which can explain the experimental observations. We developed the high-performance Al 2 O 3 TFT with 22 nm IGZO channel layer (a high mobility of 7.4 cm 2 /V, a small threshold voltage of 2.8 V, a high I on / I off 1.8 × 10 7 , and a small SS of 0.16 V/dec), which can be used as driving devices in the next-generation flat panel displays.

We have fabricated hafnium–indium–zinc-oxide (HfInZnO) thin film transistors (TFT) with indium–tin-oxide (ITO) interlayer. Compared with conventional HfInZnO-TFT, the electrical performance and bias stability of HfInZnO-TFTs with ITO interlayer are improved. HfInZnO-TFT with 4-nm-thick ITO interlayer shows a high mobility of 7.2 cm 2 /V s, a low threshold voltage of 0.13 V and a better bias stability. The performance enhancement is attributed to a decrease in interface trap state and an increase in carrier concentration. It suggests that introducing ITO interlayer at the ALD Al 2 O 3 /HfInZnO interface is an effective way to improve the electrical performance and bias stability.

Microcavity effect and pixel contrast ratio (PCR) are key issues for top-emitting organic light-emitting diode (TOLED). Si and Ag are two widely used reflective anodes for constructing effective TOLEDs. The mechanism contributing to microcavity effect and PCR has been clarified by using conventional optoelectronic theory. Consequently, the differences of microcavity effect and PCR between Si-based and Ag-based TOLEDs are discovered. Our results indicate that the Si-based TOLED possesses weak microcavity effect and improved PCR in comparison with Ag-based device. This is resulted from the low reflectivity and less reflective phase change of Si. The weak microcavity effect in Si-based TOLED also contributes to negligible variation of electroluminescent spectra with viewing angles and low device efficiency. Furthermore, Si-based TOLED shows rather high PCR which is about quintuple that of Ag-based device.

We have fabricated indium–gallium–zinc (IGZO) thin film transistor (TFT) using SiO x interlayer modified aluminum oxide (AlO x ) film as the gate insulator and investigated their electrical characteristics and bias voltage stress. Compared with IGZO-TFT with AlO x insulator, IGZO-TFT with AlO x /SiO x insulator shows superior performance and better bias stability. The saturation mobility increases from 5.6 cm 2 /V s to 7.8 cm 2 /V s, the threshold voltage downshifts from 9.5 V to 3.3 V, and the contact resistance reduces from 132 Ωcm to 91 Ωcm. The performance improvement is attributed to the following reasons: (1) the introduction of SiO x interlayer improves the insulator surface properties and leads to the high quality IGZO film and low trap density of IGZO/insulator interface. (2) The better interface between the channel and S/D electrodes is favorable to reduce the contact resistance of IGZO-TFT.

The bias stress effect in pentacene thin-film transistors (TFTs) with and without MoO x interlayer was characterized. The device without MoO x interlayer showed a large threshold voltage shift of 5.1 V after stressing with a constant gate-source voltage of −40 V for 10000 s, while at the same condition, the device with MoO x interlayer showed a low threshold voltage shift of 1.9 V. The results can be attributed to the stable interface between MoO x /pentacene and small contact resistance change for the device with MoO x /Cu electrode. Pentacene-TFTs with MoO x interlayer showed a high field-effect mobility of 0.61 cm 2 /V s and excellent bias stability, which could be a significant step toward the commercialization of OTFT technology.

In this paper, top-gate thin-film transistors (TFTs) using amorphous In–Ga–Zn–O as the n-channel active layer and SiO2 as gate insulator were fabricated by radio frequency magnetron sputtering at room temperature. In this device, a SiO layer was used to be a buffer layer between active layer and gate insulator for preventing the damage of the InGaZnO surface by the process of sputtering SiO2 with relatively high sputtering power. The thickness of buffer layers was studied and optimized for enhancing the TFTs performances. Contrasting to the TFTs without buffer layer, the optimized thickness of 10 nm SiO buffer layer improved the top-gate TFTs performances greatly: mobility increases 30%, reached 1.29 cm2/V s, the Ion/Ioff ratio increases 3 orders, and the trap density at the interface of channel/insulator decreases about 1 order, indicated that the improvement of semiconductor/dielectric interface by buffering the sputtering power.

A double hole injection layer consisting of Ag 2 O//MoO x was applied to a 4,40-bis (2,2-diphenylvinyl)-1,10-biphenyl-based blue organic light-emitting device (OLED). The hole current injection of the device was improved and the performance of the blue OLED was enhanced. We have observed that the insertion of such double layer leads to a striking improvement in chromaticity and electrical characteristics. This device showed much better chromaticity and less current-induced color shift as compared to the corresponding single hole injection layer counterparts. Using this strategy, a striking improvement in the electrical properties with lower driving voltage, higher power efficiency and a weak current-induced fluorescence quenching was achieved. This could be explained by the fact that an interlayer of Ag 2 O//MoO x provided a stepped energy level which greatly facilitated hole injection and hence enhanced injection current. The result is verified by using the J–V curves of ‘only’ devices and further explained with the help of Fowler-Nordheim (F-N) tunneling theory.

A more steric hindrance pentacene derivative, 6,13-di-(3,5-diphenyl) phenylpentacene (PDT) is synthesized in this experiment. And this manuscript presents the red emission organic light-emitting devices based on tris-(8-hydroxy- quinolinato) aluminum (Alq 3 ) co-doped with 6,13-di-(3,5-diphenyl) phenylpentacene (PDT), and 5,6,11,12-tetraphenylnaphthacene (rubrene). By measuring and analyzing the intensity of red emission and Commission Internationale de l’Eclairage (CIE) coordinates of the devices with different rubrene concentrations and thicknesses of active layer, an optimized structure of [ITO/TPD(50 nm)/Alq 3 : 3mol%PDT:1mol%rubrene(60 nm)/Bphen(25 nm)/LiF/Al] is obtained. The experimental results suggest that rubrene assists energy transfer from Alq 3 to PDT in composite of Alq 3 :PDT:rubrene, which results in relatively pure red emission. A red emission with chromaticity coordinates ( x = 0.61, y = 0.37) is also obtained with the emitting layer of [Alq 3 :3 mol% PDT:1 mol% rubrene] within the driving current density range of 12–120 mA/cm 2 . A maximum luminance efficiency of 2.4 cd/A is measured at current density of 120 mA/cm 2 and high brightness of 2894 cd/m 2 .

Bottom-contact (BC) copper phthalocyanine (CuPc) thin film transistor with UV/ozone treated Au as a source/drain electrode was fabricated and the contact resistance was estimated from the transmission line method (TLM). Comparing the properties of OTFT with untreated Au electrode, the performance of the BC CuPc-TFT with the UV/ozone treated Au electrodes was significantly improved: saturation mobility increased from 4.69 × 10−3 to 2.37 × 10−2 cm2/V s, threshold voltage reduced from −29.1 to −6.4 V, and threshold swing varied from 5.08 to 2.25 V/decade. The contact resistance of the device with UV/ozone treated Au electrodes was nearly 20 times smaller than that of the device with untreated Au electrodes at the gate voltage of −20 V. This result indicated that using the UV/ozone treated Au electrode is an effective method to reduce the contact resistance. The present BC configuration with UV/ozone treated Au electrodes could be a significant step towards the commercialization of OTFT technology.

We demonstrate p–i–n organic light-emitting diodes (OLEDs) incorporating an n-doping transport layer which comprises 8-hydroxy-quinolinato lithium (Liq) doped into 4′7-diphyenyl-1,10-phenanthroline (Bphen) as ETL and a p-doping transport layer which includes tetrafluro-tetracyano-quinodimethane (F 4 -TCNQ) doped into 4,4′,4″- tris (3-methylphenylphenylamono) triphenylamine (m-MTDATA). In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency of organic light-emitting diodes have been improved significantly after introducing a novel n-doping (Bphen: 33 wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F 4 -TCNQ as a hole transport layer (HTL). Compared with the control device (without doping), the current efficiency and power efficiency of Device C (most efficient) is enhanced by approximately 51% and 89%, respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to the efficient charge balance in the emission zone.

We demonstrated efficient red organic light-emitting diodes based on a wide band gap material 9,10-bis(2-naphthyl)anthracene (ADN) doped with 4-(dicyano-methylene)-2- t -butyle-6-(1,1,7,7-tetramethyl-julolidyl-9-enyl)-4 H -pyran (DCJTB) as a red dopant and 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1 H ,5 H ,11 H -10(2-benzothiazolyl)quinolizine-[9,9 a ,1 gh ]coumarin (C545T) as an assistant dopant. The typical device structure was glass substrate/ITO/4,4′,4″-tris( N -3-methylphenyl- N -phenyl-amino)triphenylamine ( m -MTDATA)/ N , N ′-bis(naphthalene-1-yl)- N , N ′-diphenyl-benzidine (NPB)/[ADN:Alq 3 ]:DCJTB:C545T/Alq 3 /LiF/Al. It was found that C545T dopant did not by itself emit but did assist the energy transfer from the host (ADN) to the red emitting dopant via cascade energy transfer mechanism. The OLEDs realized by this approach significantly improved the EL efficiency. We achieved a significant improvement regarding saturated red color when a polar co-host emitter (Alq 3 ) was incorporated in the matrix of [ADN:Alq 3 ]. Since ADN possesses a considerable high electron mobility of 3.1 × 10 −4 cm 2 V −1 s −1 , co-host devices with high concentration of ADN (>70%) exhibited low driving voltage and high current efficiency as compared to the devices without ADN. We obtained a device with a current efficiency of 3.6 cd/A, Commission International d’Eclairage coordinates of [0.618, 0.373] and peak λ max = 620 nm at a current density of 20 mA/cm 2 . This is a promising way of utilizing wide band gap material as the host to make red OLEDs, which will be useful in improving the electroluminescent performance of devices and simplifying the process of fabricating full color OLEDs.

This letter presents a deep blue organic light emitting diode which was fabricated by using 9,10-di(2-naphthyl)anthracene as a dopant and 4,4′- N , N ′-dicarbazole-biphenyl as a host. The Commission Internationale de l’Eclairage coordinates of (0.1516, 0.0836) were achieved in the cell, which is very close to the National Television Standards Committee standard of (0.14, 0.08). Meanwhile, maximum luminance over 6500 cd/cm 2 and maximum current efficiency of 3.5 cd/A were also obtained.

This paper presents organic light emitting diodes (OLEDs) which were fabricated by using undoped 9,10-di(2-naphthyl)anthracene (ADN) as the emitting layer, N , N ′-diphenyl- N , N ′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-amine (TPD) as the hole transporting layer, and one of tris-(8-hydroxy-quinolinato) aluminum (Alq 3 ), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 2- tert -butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) as the electron transporting layer. By optimization for the thickness of device, efficient pure blue organic light emitting diodes were obtained, which is attributed to the synergy of both the hole transporting layer and the electron transporting layer.

RGB pixels by microcavity top-emitting organic light-emitting diode (TOLED) is beneficial to both minimizing the loss of light and improving the color purity and the efficiency. Based on the multi-emitting layers, white organic light-emitting diodes (OLEDs) and microcavity TOLEDs were prepared. TOLEDs were fabricated using Ag/ITO as the reflector and adjusting layer, Al/Ag as semi-transparent cathode, Alq:DCJTB/TBADN:TBPe/Alq:C545 as white light emitting layer. By adjusting the thickness of ITO, optical length of cavity and the color of the device have been changed. So we get RGB tricolor devices. The peak wavelengths are 476 nm, 539 nm, 601 nm, Commission Internationale d’Eclairage (CIE) coordinates are (0.133, 0.201), (0.335, 0.567), (0.513, 0.360), FWHM are 32 nm, 50 nm, 73 nm for blue, green and red, respectively.

Low-voltage-drive ZnO thin-film transistors (TFTs) with room-temperature radio frequency magnetron sputtering SiO 2 as the gate insulator were fabricated successfully on the glass substrate. The ZnO-TFT operates in the enhancement mode with a threshold voltage of 4.2 V, a field effect mobility of 11.2 cm 2 /V s, an on/off ratio of 3.1 × 10 6 and a subthreshold swing of 0.61 V/dec. The drain current can reach to 1 mA while the gate voltage is only of 12 V and drain voltage of 8 V. The C–V characteristics of a MOS capacitor with the structure of ITO/SiO 2 /ZnO/Al was investigated. The carrier concentration N D in the ZnO active layer was determined, the calculated N D is 1.81 × 10 16 cm −3 , which is the typical value of undoped ZnO film used as the channel layer for ZnO-TFT devices. The experiment results show that SiO 2 film is a promising insulator for the low voltage and high drive capability oxide TFTs.