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In the work, novel indium yttrium oxide (InYO) thin films are prepared by an environmentally friendly aqueous solution process. Y element is added to suppress the generation of oxygen vacancies. The effect of Y doping on the performance and stability of nontoxic water-induced InYO thin film transistors (TFTs) is firstly examined. With the increase of Y doping contents, off-state current is decreased and mobility decreases from 15.8 to 11.7 cm2 V−1 s−1. Furthermore, the stability under positive bias stress is also obviously improved. The device with 2 mol% Y element shows an optimized electrical performance and good stability, including mobility of 12.8 cm2/V s, threshold voltage of 1.4 V, subthreshold swing of 0.33 V/decade and threshold voltage shift of 2.31 V under positive voltage stress of 5 V for 10,000 s. The performance improvement is attributed to the decrease of oxygen vacancies and the decline of interface trap density by Y addition.

Metal oxide field-effect transistors (FETs) have potential applications in display, flexible electronic device. Here, we will report the advance of our OLED display, metal oxide FETs, and application in beyond display. We have paid more attention to the stability improvement, interface trap of MO-TFT, and application in CMOS circuit, artificial synapse and gas sensor.

In this paper, boron-doped indium–zinc–oxide (InZnO) thin-film transistors (BIZO TFTs) were fabricated by solution process. The electrical performance and stability under the negative bias illumination stress (NBIS) have been greatly improved by B doping. The BIZO TFT with 5 mol.% B doping ratio shows a superior electrical performance with a field-effect mobility of 10.15 cm2/ $\textsf {V}\,\cdot \, \textsf {s}$ , a threshold voltage of 3.29 V, a subthreshold swing of 0.35 V/decade, and an ON/OFF ratio of 108. Furthermore, the 5 mol.% BIZO TFT shows only a −1.59 V shift of the threshold voltage, compared with a large negative shift of −4.24 V for pure IZO TFTs. The enhancement of electrical performance and stability under NBIS is due to the reduction of oxygen vacancies, which are suppressed by B doping. The density of states is calculated to further validate the improved electrical performance and NBIS stability of BIZO TFTs.

The high κ ZrAlOx gate insulators were deposited by atomic layer deposition on silicon and characterized by the different analytical techniques. The grazing incidence X-ray diffraction (GIXRD) verifies that ZrAlOx thin films show an amorphous structure. The X-ray photoelectron spectroscopy (XPS) confirms that the form of ZrAlOx phase improves the electrical properties and stability of the associated devices. Then, all ZrAlOx thin films were integrated in metal-insulator-semiconductor structures to check the electrical capabilities. They all show a low leakage current density (about 1 × 10−8 A/cm2) under a high electric field of about 2.0 MV/cm, and exhibit a stable capacitance as a function of frequency. Their associated ZTO TFTs were deposited by a radio frequency sputtering, and the influence of the ZrAlOx thickness on the stabilities under positive bias stress and electrical properties is investigated. The 130 nm ZrAlOx based TFT shows the optimized electrical properties (its mobility, threshold voltage, sub-threshold voltage swing and on-off ratio are 12.5 cm2/V, 0.3 V, 0.15 V/dec. and 8 × 107 and the good stability with 2.5 V threshold voltage shift under the positive bias voltage stress. The better properties of 130 nm ZrAlOx based TFTs are attributed to a less interface trap states and surface scattering center.

This work reports an efficient route for enhancing the stability of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs). It is clearly observed that the off-current in IGZO-TFT decreases by usi...

We investigate thermally induced instability of thin film transistors with incorporating sputtered InZnO and InGaZnO as the channel layer at room temperature, using density of states extracted from...

High dielectric constant TiSiOx thin films are produced by reactive sputtering under different oxygen partial pressure ratio (P O2 ) from 15% to 30%. All the TiSiOx films show an excellent transmittance value of almost 95%. The TiSiOx film has a low leakage current density by optimizing oxygen partial pressure, and the leakage current density of TiSiOx film under P O2 of 20% is 4.88×10 −7 A/cm 2 at electrical field strength of 2 MV/cm. Meanwhile, their associated InGaZnO thin-film transistors (IGZO-TFTs) with different P O2 TiSiOx thin films as gate insulators are fabricated. IGZO-TFTs under P O2 of 20% shows an optimized electrical performance, and the threshold voltage, sub-threshold swing, field effect mobility and I on /I off ratio of this device are 2.22 V, 0.33 V/decade, 29.3 cm 2 /V s and 5.03×10 7 , respectively. Moreover, the density of states (DOS) is calculated by temperature-dependent field-effect measurement. The enhancements of electrical performance and temperature stability are attributed to better active/insulator interface and smaller DOS.

The electrical degradation behavior in metal oxide thin film transistor (TFT) under negative bias-illumination stress (NBIS) is one of the biggest obstacles for its applications in flat panel display. In order to solve this issue, Sr and N are doped in In 2 O 3 thin film and significantly improve the NBIS stability of In 2 O 3 TFT. In addition, the doping of N can also reduce the degradation in electrical performance caused by Sr doping. The XPS of SrInON thin film is tested to prove the reduction of the oxygen vacancy.

The novel hafnium added ZnSnO (ZTO) thin films were deposited by a dual-target magnetron co-sputtering system. The effect of hafnium doping content on the structure, surface morphology, chemical compositions, optical and electrical properties of HZTO thin films is studied. The HZTO thin films with high hafnium content show an amorphous structure, smooth surface, less carrier concentration and wider optical bandgap. XPS results show that oxygen vacancies as electron charge carrier are effectively suppressed by increasing Hf contents. In addition, their associated application in thin film transistors (TFTs) with Al 2 O 3 gate insulator were fabricated. The interface trap states between the gate insulator and HZTO thin films become fewer with increasing the hafnium doping content. Moreover, hafnium doping content has an important influence on the electrical property and bias stability of TFTs. Although the mobility decreases with increasing the hafnium doping content, the stability is improved obviously. The improved bias stability is attributed to a fewer bulk traps in channel and interface traps between the gate insulator and channel layer, which are commonly originated from oxygen vacancies in oxide-based semiconductors. Therefore, the hafnium ion is a good electron suppressor, and the hafnium doping can effectively suppress gate bias instability of TFTs.

White organic light-emitting diodes (WOLED) with inorganic/organic/hybrid nanolaminate distributed Bragg reflector (DBR) prepared by atomic layer deposition (ALD) has been firstly developed, and the improved structural, optical, and electrical properties have been observed. The functional layer consists of periodically alternating layers of ZrO2/Zircone (zirconium alkoxides with carbon-containing backbones) films fabricated using ALD. By well adjusting the thickness and emissive dyes of the emission layer, three white light diodes were realized based on three cavity modes with different resonance wavelength and intensity. The narrowed lectroluminescent (EL) spectra from the microcavity organic light emitting diodes (MOLEDs) are of high-purity, and the off-resonant optical mode is highly suppressed due to the excellent optical properties of the DBR layers with high reflectivity in a wide stop-band range. The CIE chromaticity coordinates of devices are tuned from (0.33, 0.34), (0.43, 0.40) to (0.57, 0.40), which are all on the planckian locus, and the color temperature is adjusted from 5783 K, 3842 K to 2245 K. This work exhibits a simple and novel approach to achieve a sunlight-like WOLED by constructing the inorganic/organic nanolaminate DBR using ALD, which will be very important for healthy display and lighting.

We fabricated compounded ZrO2–Al2O3 nanolaminate dielectrics by the atomic layer deposition (ALD) and used them to successfully integrate the high-performance InZnO (IZO) thin-film transistors (TFTs). It is found that nanolaminate dielectrics combine the advantages of constituent dielectrics and produce TFTs with improved performance and stability compared to single-layer gate insulators. The mobility in IZO-TFT was enhanced about 22% by using ZrO2–Al2O3 gate insulators and the stability was also improved. The transfer characteristics of IZO-TFTs at different temperatures were also investigated and temperature stability enhancement was observed for the TFT with ZrO2–Al2O3 nanolaminates as gate insulators. A larger falling rate (∼1.45 eV/V), a lower activation energy (Ea, ∼1.38 eV) and a smaller density-of-states (DOS) were obtained based on the temperature-dependent transfer curves. The results showed that temperature stability enhancement in InZnO thin-film transistors with ZrO2–Al2O3 nanolaminate as gate insulators was attributed to the smaller DOS.

We fabricated fully transparent hafnium indium zinc oxide (HfInZnO) thin film transistors (TFTs) with ZnO:Al(AZO)/Ag/ZnO:Al multilayer source/drain (S/D) electrodes. The effect of Ag interlayer thickness on the electrical and optical properties of AZO(60 nm)/Ag/AZO(60 nm) multilayer films was investigated. The AZO(60 nm)/Ag(10 nm)/AZO(60 nm) multilayer film shows a low sheet resistance of 10.5 Ω/square and a transmittance of 87%. Compared with HfInZnO-TFT with AZO electrode, the performance of the device with AZO/Ag/AZO multilayer electrode was significantly improved. The field effect mobility increased from 3.2 to 5.8 cm 2 /V s, and the threshold voltage reduced from 2.3 to 0.1 V. The improvement was attributed to the lower resistivity of AZO/Ag/AZO multilayer film. The result indicates that AZO/Ag/AZO multilayer electrode is a promising S/D electrode for fully transparent HfInZnO-TFTs.

Amorphous LaZnSnO thin films with different La doping concentration are prepared by a combustion solution process and the electrical performances of thin film transistors (TFTs) are investigated. The influence of La content on the structure, oxygen vacancies, optical and electrical performance of LaZnSnO thin films are investigated. At an appropriate amount of La doping (15 mol.%), LaZnSnO-TFT shows a superior electrical performance including a mobility of 4.2 cm2/V s, a subthreshold swing of 0.50 V/decade and an on/off current ratio of 1.9 × 107. The high performance LaZnSnO-TFT is attributed to the better interface between SiO2 and LaZnSnO channel layer and the suppression of oxygen vacancies by optimizing La content. It suggests that La doping can be a useful technique for fabricating high performance solution-processed oxide TFTs.

In this work, we report the influence of ZnSnO channel layer sputtering power in the stability of ZnSnO TFTs under negative gate-bias illumination stress (NBIS). The origin of threshold voltage shift results from combined effect of two factors between the little defect-induced trap densities originated from oxygen vacancies and better channel–insulator interface. The kinetic energy of the ions at a proper rf sputtering power is responsible for less defect-induced trap density and better channel–insulator interface. Therefore, the ZnSnO TFT fabricated at 75 W sputtering power shows a better NBIS stability. In addition, the trap density is extracted by temperature-dependent field-effect measurements and it is consistent with the change of stability under NBIS and thermal stress.

Graphical abstract: This work reports the Ba content on thin film transistor based on a novel BaZnSnO semiconductor using solution process. - Highlights: • No reports about BaZnSnO thin film using solution process. • BaZnSnO thin film transistor (TFT) was firstly fabricated. • BaZnSnO-TFT shows a acceptable performace. • Influence of Ba content on BaZnSnO-TFT. - Abstract: A novel BaZnSnO semiconductor is fabricated using solution process and the influence of Ba addition on the structure, the chemical state of oxygen and electrical performance of BaZnSnO thin films are investigated. A high performance BaZnSnO-based thin film transistor with 15 mol% Ba is obtained, showing a saturation mobility of 1.94 cm{sup 2}/V s, a threshold voltage of 3.6 V, an on/off current ratio of 6.2 × 10{sup 6}, a subthreshold swing of 0.94 V/decade, and a good bias stability. Transistors with solution processed BaZnSnO films are promising candidates for the development of future large-area, low-cost and high-performance electronic devices.

We investigate the stability of thin film transistors incorporating sputtered InZnO as the channel layer under negative bias illumination stress. The transfer characteristic for various active layer thicknesses is shifted toward the negative direction under negative bias illumination stress and the device with thicker channel layer shows a slighter V TH negative shift than another device under negative bias illumination stress. In order to investigate channel layer thickness can have a great effect on the trap density and thus affect the V TH shift caused by charge trapping; we use temperature-dependent field-effect measurements method to accurately calculate their trap density. The results show that thicker InZnO channel layer has fewer DOSs, resulting in the decrease of charge trapping and the decrease of photoexcitation generated electron carrier. So the device with thicker channel layer shows a slighter V TH negative shift than another device under negative bias illumination stress.

Top-contact thin-film transistors (TFTs) are fabricated in this work using atomic layer deposition (ALD) Al2O3 as the gate insulator and radio frequency sputtering InGaZnO (IGZO) as the channel layer so as to investigate the effect of Al2O3 thickness on the performance of IGZO-TFTs. The results show that TFT with 100-nm-thick Al2O3 (100 nm-Al2O3-TFT) exhibits the best electrical performance; specifically, field-effect mobility of 5 cm2/Vs, threshold voltage of 0.95 V, Ion/Ioff ratio of 1.1×107 and sub-threshold swing of 0.3 V/dec. The 100 nm-Al2O3-TFT also shows a substantially smaller threshold voltage shift of 1.1 V after a 10 V gate voltage is applied for 1 h, while the values for TFTs with an Al2O3 thickness of 220 and 280 nm are 1.84 and 2 V, respectively. The best performance of 100 nm-Al2O3-TFT can be attributed to the larger capacitance and the smaller amount of total trap centers possessed by a thinner insulator compared to the thicker ones.

We have fabricated novel BaZnSnO-TFT using a solution process and investigated the electrical performance and temperature stability. BaZnSnO-TFT shows an improved field-effect mobility of 3.2 cm2 V−1 s−1, a subthreshold swing of 0.61 V per decade and an on/off current ratio of 2 × 107 compared to those of ZnSnO-TFT. Density of state distribution of BaZnSnO and ZnSnO semiconductor has been extracted from electrical measurements. BaZnSnO-TFT shows an improved electrical performance and temperature stability due to smaller oxygen vacancies, less bulk trap density and interface state density.

Thin film transistors (TFTs) with bottom gate and staggered electrodes using atomic layer deposited Al 2 O 3 as gate insulator and radio frequency sputtered In–Ga–Zn Oxide (IGZO) as channel layer are fabricated in this work. The performances of IGZO TFTs with different deposition temperature of Al 2 O 3 are investigated and compared. The experiment results show that the Al 2 O 3 deposition temperature play an important role in the field effect mobility, I on / I off ratio, sub-threshold swing and bias stability of the devices. The TFT with a 250 °C Al 2 O 3 gate insulator shows the best performance; specifically, field effect mobility of 6.3 cm 2 /Vs, threshold voltage of 5.1 V, I on / I off ratio of 4×10 7 , and sub-threshold swing of 0.56 V/dec. The 250 °C Al 2 O 3 insulator based device also shows a substantially smaller threshold voltage shift of 1.5 V after a 10 V gate voltage is stressed for 1 h, while the value for the 200, 300 and 350 °C Al 2 O 3 insulator based devices are 2.3, 2.6, and 1.64 V, respectively.

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 successfully integrated the high-performance oxide thin film transistors with novel IZO/IGZO dual-active-layers. The results showed that dual-active-layer (IZO/IGZO) TFTs, compared with single active layer IGZO TFTs and IZO TFTs, exhibited the excellent performances; specifically, a high field effect mobility of 14.4 cm2/Vs, a suitable threshold voltage of 0.8 V, a high on/off ratio of more than 107, a steep sub-threshold swing of 0.13 V/dec, and a substantially small threshold voltage shift of 0.51 V after temperature stress from 293 K to 353 K. In order to understand the superior performance, the density-of-states (DOS) were investigated based on the temperature-dependent transfer curves. The superior electric properties were attributed to the smaller DOS and higher carrier concentration. The proposed IZO/IGZO-TFT in this paper can be used as driving devices in the next-generation flat panel displays.

A high-performance InGaZnO (IGZO) thin-film transistor (TFT) with ZrO 2 –Al 2 O 3 bilayer gate insulator is fabricated. Compared to IGZO-TFT with ZrO 2 single gate insulator, its electrical characteristics are significantly improved, specifically, enhancement of I on / I off ratios by one order of magnitude, increase of the field-effect mobility (from 9.8 to 14 cm 2 /Vs), reduction of the subthreshold swing from 0.46 to 0.33 V/dec, the maximum density of surface states at the channel-insulator interface decreased from 4.3 × 10 12 to 2.5 × 10 12 cm − 2 . The performance enhancements are attributed to the suppression of leakage current, smoother surface morphology, and suppression of charge trapping by using Al 2 O 3 films to modify the high- k ZrO 2 dielectric.

Top-contact thin-film transistors (TFTs) are fabricated in this work by using radio frequency sputtering InZnO (IZO) as the channel layer so as to investigate the effect of working power densities ( P d ) on the performance of IZO-TFTs. Good-quality Al 2 O 3 thin films that are used as gate insulators are deposited via atomic layer deposition (ALD) technique. The results show that TFT with a P d of 1 W/cm 2 exhibits the best electrical performance; specifically, field-effect mobility of 17.9 cm 2 /V s, threshold voltage of −0.46 V, on/off ratio of 10 8 and sub-threshold swing of 0.13 V/dec. In order to understand the superior performance, the density-of-states (DOS) were investigated based on the temperature-dependent transfer curves. The investigation shows that the sputtering power density has significant effect on DOS of channel layer. The superior electric properties were attributed to the smaller DOS.

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.

We investigate the electrical performance and negative bias stability of thin film transistors (TFTs) using double active layer. Double active layer is consisting of low oxygen content HfInZnO film as bottom channel and high oxygen content HfInZnO film as back channel. The HfInZnO-TFT with double channel layer shows a high mobility of 6.8 cm2/V s, a low threshold voltage of − 0.3 V, and a threshold voltage shifts of 0.65 V under − 20 V gate bias for 7200 s. The results suggest that HfInZnO with low oxygen content as the bottom channel could provide high carrier concentration and good HfInZnO/Al2O3 interface to improve field-effect mobility and negative bias stress stability. HfInZnO with high oxygen content as back channel can control the conductivity to reduce the off current of TFT. Thus, a double-active-layer structure is an effective way to improve the electrical performance of HfInZnO-TFT.

High-performance thin-film transistors (TFTs) using atomic layer deposited (ALD) Al 2 O 3 as gate insulator and radio frequency (RF) sputtering In–Ga–Zn Oxide (IGZO) as channel layer were fabricated in this work. A SiO 2 buffer layer was applied between IGZO and Al 2 O 3 to prevent the picked-up defects when the samples were switched from ALD to RF sputtering. Contrasting to the TFTs without buffer layer, the SiO 2 buffer layer improved the TFTs performances greatly, such as: the field effect mobility increases from 5.2 cm 2 /V s to 6.1 cm 2 /V s, the threshold voltage downshifts from 4.9 V to 1.7 V, the I on / I off ratio increases from 2.8 × 10 7 to 9.6 × 10 7 , the sub-threshold swing decreased from 0.76 V/dec to 0.6 V/dec. The maximum density of surface states at the channel–insulator interface decreased from 2.1 × 10 12 cm − 2 to 1.53 × 10 12 cm −2 .

We reported on the electrical and surface characteristics of radio frequency (rf) AlO x film and their applications in InGaZnO-based thin film transistors (TFTs). By optimizing the rf power, AlO x film with the low leakage current density and smooth surface was obtained. The leakage current density for the 180 W AlO x film was observed to be ∼2.0 × 10 −9 A/cm 2 at electrical field strength of 2 MV/cm. The root mean square (rms) roughness of 180 W AlO x film was about 1.36 nm. InGaZnO-TFTs with different AlO x insulators were fabricated. The InGaZnO-TFT with 180 W AlO x insulator exhibits a field-effect mobility of 6.9 cm 2 /V s, a threshold voltage of 4.2 V, an on/off ratio of 2.7 × 10 7 , and a much smaller V th shift of 6.6 V for 20 V bias stress duration of 10,800 s. The improvement of InGaZnO-TFT with 180 W AlO x film is attributed to smooth surface of AlO x film and smaller trap charges. The results indicate that AlO x is a promising candidate insulator for InGaZnO-TFTs.

We report on the electrical properties of bottom-gate InGaZnO (IGZO) thin film transistors (TFTs) with different channel layer thicknesses. The IGZO channel layer with thickness varied from 25 to 120 nm were deposited by radio frequency sputtering. Al2O3 films were deposited on highly-doped n-Si substrate by atomic layer deposition (ALD) as gate insulator in this work. The influence of the IGZO channel layer thickness on the performance of TFTs is studied. The performance of devices is found to be thickness dependent. The best performance of devices is obtained from a 58 nm thick IGZO TFT, which shows a field-effect mobility in the saturation region of 6.2 cm2/Vs, a threshold voltage of 2.1 V, an Ion/Ioff ratio of approximately 6.4 × 107, and a subthreshold swing of 0.6 V/dec.

Thin-film transistors (TFTs) with atomic layer deposition (ALD) HfZnO (HZO) as channel layer and Al2O3 as gate insulator were successfully fabricated. Compared with ZnO-TFT, the stability of HZO-TFT was obviously improved as Hf doping can suppress the generation of oxygen related defects. The transfer characteristics of TFTs at different temperatures were also investigated, and temperature stability enhancement was observed for the TFT with Hf doping. The density of states (DOS) was calculated based on the experimentally obtained E a, which can explain the experimental observation. A high-field effect mobility of 9.4 cm2/Vs, a suitable turn-on voltage of 0.26 V, a high on/off ratio of over 107 and a steep sub-threshold swing of 0.3 V/decade were obtained in HZO-TFT. The results showed that temperature stability enhancement in HfZnO thin-film transistors are attributed to the smaller DOS.

We demonstrated a highly efficient inverted top-emitting organic light-emitting diode (ITOLED) by using Ag/Al bilayer reflective cathode and CsOx electron-injection layer. With tris(8-hydroquinoline) aluminum as electron-transport and emitting layer, the maximum luminous efficiency and power efficiency of ITOLED with CsOx electron-injection layer reached 8.3 cd/A and 4.3 lm/W, respectively, which have been enhanced by ∼40% and ∼80%, respectively, in comparison with the counterpart using LiF as electron-injection layer (5.9 cd/A and 2.3 lm/W). The improved performance is resulted from the enhanced electron-injection ability of CsOx. The superior electron-injection ability of CsOx was further verified by ‘Electron-only’ device using current density versus voltage characteristics and impedance spectroscopy measurements. Our results indicated that CsOx electron-injection layer combined with Ag/Al bilayer reflective cathode provides a convenient approach for constructing highly efficient ITOLED.

The thin-film transistors (TFTs) with InGaZnO active layer with different oxygen partial pressures are fabricated by radio frequency sputtering. The influence of the oxygen partial pressure on the density of states (DOS) for InGaZnO-TFT is investigated by using temperature-dependent field-effect measurements. It indicates that the DOS become smaller with increasing oxygen partial pressure. The results are verified by the threshold voltage shift of InGaZnO-TFT with different oxygen partial pressures. The trend of the variation of DOS is consistent with that of the threshold voltage shift for InGaZnO-TFT. Thus, the gate bias instability is attributed to the charge trapping mechanism based on DOS. Therefore, this work offered a brief and accurate method to calculate DOS for demonstrating the bias stability of transistor.

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.

We fabricated the indium-gallium-zinc oxide (IGZO) thin film transistor (TFT) with reactive sputtered SiOx as passivation layer, and investigated the role of the SiOx passivation layer in the IGZO-TFT under gate bias stress. The bias stability of IGZO-TFT with passivation layer is much better than that of IGZO-TFT without passivation layer. After applying positive bias stress of 20 V for 10000s, the device without passivation layer shows a larger positive Vth shift of 7.3 V. However, the device with passivation layer exhibits a much smaller Vth shift of 1.3 V. It suggests that Vth instability is attributed to the interaction between the exposed IGZO back surface and oxygen in ambient atmosphere during the positive gate voltage stress. The results indicate that reactive sputtered SiOx passivation layer can effectively improve the bias stability of IGZO-TFT.

A copper phthalocyanine (CuPc) organic semiconductor is capped onto an amorphous indium–gallium–zinc-oxide (InGaZnO) thin film transistor (TFT) to enhance the photosensitivity of InGaZnO-TFT. The CuPc organic semiconductor is served as a light absorption layer and forms a p – n junction with the InGaZnO film. After 60 s white light illumination, light responsivity ( R ) of InGaZnO-TFT with a CuPc light absorption layer reaches a value of 148.5 A/W at a gate-source voltage ( V GS ) of 20 V, which is much larger than that (31.2 A/W) of the conventional InGaZnO-TFT. The results are attributed to the following mechanism. First, a CuPc layer is employed as the light absorption layer. Second, CuPc/InGaZnO p – n junction enables the injection of electron into InGaZnO film. Our results indicate that using CuPc as light absorption layer is an effective approach to improve the photosensitivity of InGaZnO-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.

A comparative study on top-emitting organic light-emitting diodes (TOLEDs) with normal and inverted structures is briefly investigated. In comparison with the normal TOLED having Ag reflective anode, the inverted device with monolayer Al reflective cathode shows low efficiency as a result of lower reflectance of Al and inferior electron injection. Using Ag/Al bilayer reflective cathode is demonstrated to be a simple and effective method of enhancing efficiency in inverted TOLED. With tris(8-hydroquinoline) aluminum (Alq3) as emitter the luminous efficiency reaches 5.97 0.6 cd/A, which is much higher than those of the corresponding normal TOLED (� 5.1 cd/A) and inverted TOLED with monolayer Al reflective cathode ( � 4 cd/A). The improved performance is attributed to the enhanced reflectance and significant microcavity effect. The electron-injection barrier height of � 0.1 eV from Al to Alq3 via an ultrathin LiF is estimated in the tunneling process for both normal and inverted devices.

Fluorescent white organic light-emitting diodes (WOLEDs) with single-emitting layer (EML) and double-EML structures were demonstrated using a 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10(2-benzothiazolyl)quinolizine-[9,9a,1gh]coumarin (C545T) doped emitting system. With the incorporation of double-EML structure, white emission with Commission Internationale de L'Eclairage (CIE) color coordinates of (0.331, 0.335) and luminous efficiency of 8.04 cd/A was obtained. Moreover, WOLED with a single-EML structure shows superior electroluminescence performances such as lower voltage, higher luminance, and enhanced power efficiency. These improvements are attributed to its high energy transfer ability via the intermediation of C545T. The Forster's radius was given to clarify the actual energy transfer process.

A white organic light-emitting device (WOLED) using tris(8-hydroxyquinoline)aluminum (Alq3) as the green emission is demonstrated. Our experiments indicate that Alq3 doping not only improves the color coordinates and color stability, but also reduces current-induced fluorescence quenching. A maximum luminous efficiency of 8.87 cd/A and an applicable value of 7.92 cd/A at 20 mA/cm2 are obtained. The excellent performance predominantly results from the effective energy transfer in the emitting system and the efficient utilization of Alq3 green emission. For comparison, WOLEDs with different components as the green emission and without the component of green emission are also fabricated and investigated. Our results show that the introduction of green emission from an appropriate component significantly improves the device efficiency and color properties. This result is further verified on the basis of the theory of exciton generation and diffusion.

Based on two aggregation-induced light-emitting materials, N-(4-(benzo[d]thiazol-2-yl)-3-hydroxyphenyl) anthracene-9-carboxamide for yellow emission and N-(4-(benzo[d]oxazol-2-yl)-4-tert-butylbenzamide for Blue emission, non-doped white organic light-emitting diodes have been realized. The maximum efficiency of 2.2 cd/A and the Commission International de L'Eclairage coordinates of (0.32, 0.33) are achieved. Moreover, the device efficiency and color coordinates change slightly with increasing driving current density up to 500 mA/cm2, showing a good color stability and a small efficiency roll-off. This may due to both better confinement of excitons within the emitting layer and the utilization of a thin layer of emitting material with aggregation-induced emission.

The feasibility of using Cu as reflective anode for constructing efficient top-emitting organic light-emitting diode (TOLED) has been demonstrated. The MoOx modification can considerably enhance the work function of Cu anode, which contributes to the improvement of hole injection and thereby promoting device efficiency. In comparison with the TOLED having conventional Ag anode, the device having Cu anode shows inferior efficiency partially resulted from low reflectance of Cu, but the TOLED with Cu anode takes many advantages such as low-cost fabrication, enhanced pixel contrast ratio, weak microcavity effect and reduced leakage current. These improved performances are of great importance for practical applications, suggesting that Cu provides an alternative approach for realizing TOLED-based applications.

We demonstrated the tunable contact resistance in pentacene thin film transistor (TFT) by inserting an organic–inorganic hybrid interlayer between Au electrode and pentacene layer. The contact resistance of pentacene-TFT varies with concentration of pentacene-TFT varies with concentration of MoO x in organic–inorganic hybrid interlayer. MoO x in organic–inorganic hybrid interlayer. The contact resistance of the device with 55 wt% MoO x doped pentacene interlayer is about 7.8 times smaller than that of device without interlayer at the gate voltage of −20 V. Comparing the properties of pentacene-TFT without interlayer, the performance of the pentacene-TFT with 55 wt% MoO x doped pentacene was significantly improved: saturation mobility increased from 0.39 to 0.87 cm 2 /V s, threshold voltage reduced from −21.3 to −7.2 V, and threshold swing varied from 3.75 to 1.39 V/dec. Our results indicated that the organic–inorganic hybrid interlayer is an effective way to improve the performance of p -channel OTFTs.

This work demonstrated the fabrication of white organic light-emitting devices (WOLEDs) using a dual emitting layer (d-EML) consisting of blue and ‘white’ emitters. In this d-EML system, the blue emitter not only emits but also assists the incomplete energy transfer. More importantly, it behaves as an effective trapping site for holes, which contributes to the efficient recombination of electron–hole pairs. The d-EML was constructed between the hole-transmitting layer (HTL) and the electron-transmitting layer (ETL) of Alq 3 and BPhen. The thickness of the blue emitter used in the d-EML devices has an important effect on chromaticity and efficiency. Through the optimization of device structure, the reasonable white emission with Commission Internationale de L’Eclairage (CIE) color coordinates of (0.33, 0.33) and little color shift was obtained. The device showed an applicable luminance with its maximum luminance of 22,874 cd/m 2 at a driving voltage of 16 V. The maximum luminance efficiency was achieved 8.10 cd/A, and the maximum power efficiency was reached 5.07 Lm/W. The result is explained with the help of the excitons generation and diffusion theory. According to the theory of excitons generation and diffusion, an equation has been set up which concerns electroluminescent spectra to the thickness of the two emitters and to the exciton diffusion length.

High efficiency fluorescent white organic light-emitting device (WOLEDs) was investigated by using a double-graded (DG) structure. This strategy can greatly improve the device performances such as better color stability, higher luminance and enhanced efficiency. The optimized WOLED gives the Commission Internationale de L’Eclairage (CIE) color coordinates of (0.324, 0.341) at 20 mA/cm 2 , a negligible color shift of Δ x , y = ±[0.000.001] from 4 to 200 mA/cm 2 , a maximum brightness of 39,740 cd/m 2 at 17 V and a maximum luminance efficiency of 11.5 cd/A at 16 V. In addition, current-induced fluorescence quenching is mostly controlled.

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.

Organic light-emitting devices (OLEDs) with MoOx, Ag2O and a composite layer consisting of Ag2O//MoOx as hole injection layers (HIL) have been investigated. We have observed that the insertion of such a composite layer leads to a striking improvement in the electrical properties with lower driving voltage, higher power and current efficiencies. At a current density of 20 mA/cm2, the driving voltage of the device using an Ag2O//MoOx composite HIL (Cell-AM) is 5.9 V, which is 2.2 V, 3.8 V and 4.5 V lower than that of the devices using MoOx (Cell-M), Ag2O (Cell-A) as HIL and the device (Cell-I) without HIL, respectively. Its power efficiency is 2.56 Lm/W, which is 1.8, 2.4 and 3.6 times higher than that of Cell-M, Cell-A, and Cell-I, respectively. The current efficiency is 4.88 cd/A, which is 33.7%, 58.4% and 110.3% higher than Cell-M, Cell-A, and Cell-I, respectively. These improvements are attributed to its high hole injection ability. The result is verified by using the J – V curves of ‘only’ devices and further explained with the help of the Fowler–Nordheim (F–N) tunneling theory.

An n + -doped-layer-free microcrystalline silicon thin-film transistor (μc-Si TFT) with Al alloy as the source/drain (S/D) electrode was fabricated and investigated. The device showed a field-effect mobility of 0.28 cm 2 /V s and a threshold voltage of 5.3 V. The mobility measured in the linear regime was found to be roughly similar to that calculated in the saturation regime for the same device. Compared to a μc-Si TFT with an n + -doped layer, the μc-Si TFT with Al alloy as the S/D electrode exhibited similar electrical performance. This indicated that a good contact exists between the Al-alloy film and microcrystalline silicon. Our result also showed that using Al alloy as the S/D electrode is an effective way to substitute the n + -doped layer in a μc-Si TFT.