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In this work, a water/alcohol-soluble conjugated polymer poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9–dihexylfluorene)] (PFNC6) is synthesized and the photophysical properties are investigated. Subsequently, it is tested as electron injection layer in a blue emitting OLED with PFO. The maximum current efficiency (CE) and external quantum efficiency (EQE) of the device increased by 3 times to 0.75 cd/A and 0.66%. Further enhancement in the OLED performance is obtained when a bilayer electron injection consisting of PFNC6 and LiF are used where the maximum CE is 2.16 cd/A and the maximum EQE is 1.55%. Measurement with electron-only-devices confirmed that the electron mobility is increased for the device with PFNC6 as compared to the control device. Furthermore, higher Vbi is obtained in photovoltaic measurement when PFNC6 is used. As a result, the electron injection barrier is reduced and electron injection is more efficient.

The plasma characteristics of 355 nm and 532 nm laser ablation of Al-doped ZnO (AZO) target were studied by optical emission spectroscopy and ion probe measurements. Zn emission lines were measured detected at above 0.9 J/cm 2 for 355 nm laser and 0.6 J/cm 2 532 nm laser respectively, while Al species were detected only above 2 J/cm 2 . The kinetic energy of the ions was slightly higher for 532 nm ablation as compared to 355 nm ablation. In addition, the ablation of 532 nm laser was affected by the large laser penetration depth. When deposited at 2 and 4 J/cm 2 , AZO films with energy band gap of 3.45–3.6 eV were obtained. Nanostructured AZO films were obtained by 355 nm laser ablation but nano and micro-particulates were formed in 532 nm laser ablation. The large micron-sized particulates were Al-rich thus affecting not only the morphology but also the stoichiometry of the films. It is thus concluded that despite a lower ablation and growth rate, 355 nm generated Zn, O and also Al species at lower threshold fluence that can lead to high quality AZO films at room temperature.

Background gases (O2, He or Ar) with the pressure from ~ 10−3 Pa to 133.3 Pa are used in 355 nm laser deposition of Al-doped ZnO at room temperature. The effects of these gases and pressure on plasma formation are studied by optical emission spectroscopy (OES) and time of flight (TOF) measurement. The OES results show that the emission intensity of the species in O2 and Ar decrease slightly and then increase exponentially above ~ 5 Pa. The emission intensity in Ar is the highest, followed by emission in O2 whilst the emission in He is low and weakly depend on background gas pressure. TOF measurements indicate that the ion velocity decrease with increasing O2 and Ar pressure at about 5–10 Pa. The ion velocity is highest in He while the ion velocities in O2 and Ar are similar. Thin-film samples deposited in different gas at 2.6 Pa are amorphous, but those deposited at 133.3 Pa are crystalline and exhibit different morphologies and optical properties depending on type of gas. Samples deposited in O2 are highly transparent but those deposited in He and Ar contain nano and micron-sized structures with

In this work, we investigated on the growth of Cu 2 ZnSnS 4 films by using pulsed Nd:YAG laser (355 nm) ablation of a quaternary Cu 2 ZnSnS 4 target. Depositions were performed at laser fluence from 0.5 to 4 J cm −2 . The films were grown at substrate temperature from 27 °C to 300 °C onto glass and silicon substrates. The dependence of the film morphology, composition, and optical properties are studied and discussed with respect to laser fluence and substrate temperature. Composition analysis from energy dispersive X-ray spectral results show that CZTS films with composition near stoichiometric were obtained at an optimized fluence at 2 J cm −2 by 355 nm laser where the absorption coefficient is >10 4 cm −1 , and optical band gap from a Tauc plot was ∼1.9 eV. At high fluence, Cu and Sn rich droplets were detected which affect the overall quality of the films. The presence of the droplets was associated to the high degree of preferential and subsurface melting on the target during high fluence laser ablation. Crystallinity and optical band gap (1.5 eV) were improved when deposition was performed at substrate temperature of 100 °C.

Al-doped ZnO (AZO) thin films were deposited on p-Si (100) by pulsed laser deposition from a composite ceramic target (ZnO:Al2O3) by using 355 nm laser at different O2 background pressure and substrate temperature. Upon ablation at laser fluence of 2 Jcm−2, plasma plume consists of Zn neutrals and ions, Al neutrals and O neutral are formed. As the O2 background pressure increases from 3 Pa to 26 Pa, the energy of the plasma species are moderated. The results show that the ions density and velocity reduced significantly above 13 Pa. The velocity of the ions reduced from 14 kms−1 to 11 kms−1 at 13 Pa, while the ions energy reduced from 63 eV to 42 eV respectively. Below 13 Pa, crystalline and homogeneous AZO nanostructured films were formed. Above 13 Pa, the process results in low crystallinity films with higher porosity. The resistivity of the films also increases from 0.1 ohmcm to 24 ohmcm as the pressure increased. At fixed O2 background pressure of 3 Pa, the adatom mobility of atoms on the substrates is altered by substrate heating. The resistivity of the films decreased to 10–3 ohmcm when the substrates are heated to 100 °C–300 °C during deposition. The films with highest carrier density of 1020 cm−3 and carrier mobility of 13 cmV−1 s−1 are achieved at 200 °C.

The generation of a homogeneous plasma plume is necessary for the pulsed laser deposition of thin films. In this work, we investigate the effects of nanosecond-duration laser pulses to ablate polycrystalline Si targets in vacuum ( −4 Pa) at room temperature. The laser wavelength covers the range from ultra-violet to infrared by using a KrF (248 nm, 25 ns) and a Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) laser. The films were deposited at laser fluences from 1 to 6 J/cm 2 and characterized by atomic force microscopy and spectroscopic ellipsometry. Time-integrated optical emission spectra were obtained for excited neutrals and ionized Si species in the plasma produced between 0.5 and 11 J/cm 2 . The relation between the ionized species and film properties were discussed.

In this work, we investigated the laser ablation and deposition of Si and Ge at room temperature in vacuum by employing nanosecond lasers of 248 nm, 355 nm, 532 nm and 1064 nm. Time-integrated optical emission spectra were obtained for neutrals and ionized Ge and Si species in the plasma at laser fluences from 0.5 to 11 J/cm2. The deposited films were characterized by using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Amorphous Si and Ge films, micron-sized crystalline droplets and nano-sized particles were deposited. The results suggested that ionized species in the plasma promote the process of subsurface implantation for both Si and Ge films while large droplets were produced from the superheated and melted layer of the target. The dependence of the properties of the materials on laser wavelength and fluence were discussed.

Nickel (Ni) thin films were deposited on glass substrates in high vacuum and at room temperature with third-harmonic or 355-nm output from a nanosecond Nd:YAG laser. At low laser fluence of 1 J/cm2, the deposition rate was about 0.0016 nm/shot which increased linearly until 4 J/cm2. Above 4 J/cm2, the onset of phase explosion in the ablation abruptly increased the optical emission intensity from laser-produced Ni plume as well as thin-film deposition rate by about 6×. The phase explosion also shifted the size distribution and number density of Ni droplets on its thin-film surface. On the other hand, the surface structures of the ablated Ni targets were compared between the scan-mode and the fixed-mode ablations, which may suggest that droplets observed on the thin-film surface were caused by direct laser-induced splashing of molten Ni rather than vapour-to-cluster condensation during the plume propagation.

Effects of O 2 , N 2 , Ar and He on the formation of micro- and nanostructured indium tin oxide (ITO) thin films were investigated in pulsed Nd:YAG laser deposition on glass substrate. For O 2 and Ar, ITO resistivity of ≤ 4 × 10 -4 Ωcm and optical transmittance of > 90% were obtained with substrate temperature of 250 °C. For N 2 and He, low ITO resisitivity could be obtained but with poor optical transmittance. SEM images show nano-structured ITO thin films for all gases, where dense, larger and highly oriented, microcrystalline structures were obtained for deposition in O 2 and He, as revealed from the XRD lines. EDX results indicated the inclusion of Ar and N 2 at the expense of reduced tin (Sn) content. When the ITO films were applied for fabrication of organic light emitting devices (OLED), only those deposited in Ar and O 2 produced comparable performance to single-layer OLED fabricated on the commercial ITO.

Nanowires of indium tin oxide (ITO) were grown on catalyst-free amorphous glass substrates at relatively low temperature of 250 °C in argon and helium ambient by the Nd:YAG pulsed laser deposition technique. All the ITO samples showed crystalline structure due to substrate heating and the (400) X-ray diffraction peak became relatively stronger as the pressure was increased. The surface morphology was also changed from compact, polycrystalline thin-film layers to a dendritic layer consisting of nanowires for some limited pressure ranges. The transition from the normal thin-film structure to nanowires was likely due to the vapor–liquid–solid mechanism but under catalyst-free condition. These nanowires tended to grow perpendicularly on the glass substrate, as observed with the transmission electron microscopy (TEM), which also confirmed that these nanowires were crystalline.