RESUMEN

Cu(InxGa1-x)Se2(CIGS) precursor films were prepared on ITO glass with potentiostatic electrodeposition. High quality CIGS films were obtained by selenization of the precursor films at high temperature in tubular furnace full of argon gas. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis-NIR spectroscopy were used to characterize the structure, morphology, composition and Vis-NIR absorption of CIGS films, respectively. XRD results show the selenized CIGS films have a preferential orientation (112) with average crystallite of 24.7 nm. Raman spectroscopy reveals that the CIGS films are pure quaternaryphases with chalcopyrite structure, and without binary or ternary phases in the films. Vis-NIR measurements determine that the bandgap of CIGS increases with the increase of Ga concentration in the film. When the Ga concentration is 5.41%, its bandgap is about 1.11 eV, and the calculated ratio of Ga to (Ga+In) is 16.3%, which is less than the ratio of Ga to (Ga+In), 21.4%, measured by SEM. This indicates that crystallinity of CIGS filmsneeds to be further improved. All the measurements demonstratethat optimum ITO/CIGS has a promising application in bifacial solar cells. In this paper, we provide a newmethodtoelectrodeposit low cost CIGS precursor films and a new method forselenization ofthe precursor films at high temperature. As a result, theuniform and compact CIGS films with good adhesion on ITO are successfully fabricated by these methods. The above characterization show that we have obtained CIGS films with high crystallinity, near stoichiometry, few impurity phases and superior light absorption. Electrodeposition, like magnetron sputtering, is very suitable for large-scale industrial production. The research work in this paper is therefore important and considerable to massive production of electrodeposition of CIGS films.

RESUMEN

Cu(InxGa1-x)Se2(CIGS) precursor films were prepared on ITO glass with potentiostatic electrodeposition. High quality CIGS films were obtained by selenization of the precursor films at high temperature in tubular furnace full of argon gas. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis-NIR spectroscopy were used to characterize the structure, morphology, composition and Vis-NIR absorption of CIGS films, respectively. XRD results show the selenized CIGS films have a preferential orientation (112) with average crystallite of 24.7 nm. Raman spectroscopy reveals that the CIGS films are pure quaternaryphases with chalcopyrite structure, and without binary or ternary phases in the films. Vis-NIR measurements determine that the bandgap of CIGS increases with the increase of Ga concentration in the film. When the Ga concentration is 5.41%, its bandgap is about 1.11 eV, and the calculated ratio of Ga to (Ga+In) is 16.3%, which is less than the ratio of Ga to (Ga+In), 21.4%, measured by SEM. This indicates that crystallinity of CIGS filmsneeds to be further improved. All the measurements demonstratethat optimum ITO/CIGS has a promising application in bifacial solar cells. In this paper, we provide a newmethodtoelectrodeposit low cost CIGS precursor films and a new method forselenization ofthe precursor films at high temperature. As a result, theuniform and compact CIGS films with good adhesion on ITO are successfully fabricated by these methods. The above characterization show that we have obtained CIGS films with high crystallinity, near stoichiometry, few impurity phases and superior light absorption. Electrodeposition, like magnetron sputtering, is very suitable for large-scale industrial production. The research work in this paper is therefore important and considerable to massive production of electrodeposition of CIGS films.

RESUMEN

Thin films of cadmium sulfide (CdS) were prepared with ammonium chloride, cadmium chloride, potassium hydroxide and thiourea by chemical bath deposition (CBD). For comparison, CdS films were also deposited by radio frequency (RF) magnetron sputtering, using CdS and argon as a target and reactive gas, respectively. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible spectroscopy. The results show that the CdS films prepared by the above two methods have (002) orientation, the CdS films deposited by RF magnetron sputtering are more compact and much smoother than those prepared by CBD, and have lager crystalline size of about 20-30 nm. The CdS films prepared by CBD have smaller crystalline size and more defects. The properties of CdS thin films prepared by RF magnetron sputtering are totally superior to those of CdS films by CBD, but the optical transmittance of CdS thin films at short wavelength is an exception. The energy gap of CdS films prepared by the two methods are all in the range of 2.3-2.5 eV.

RESUMEN

In the present paper, the electroluminescence emission from a doped polymer layer was studied. The blue fluorene PFO was used as the host material and MEH-PPV as the dopant. The spectral characteristics and color stability of the emission on CIE chromaticity diagram were investigated. With the doping ratio of 2.5 Wt%, the device shows turn-on voltage of 3 V, and color coordinates of (0.33, 0.33) at 11 V. The color coordinates of the device was stable with changing voltage in a large range, and located in the ideal white area in the range of 5-20 V voltage.

RESUMEN

Four organic solar cells with the different structures were fabricated. The structures are Device1 ITO/LiF/PEDOT: PSS/MEH-PPV/C60/Al, Device 2 ITO/PEDOT : PSS/MEH-PPV/C60/Al, Device 3 ITO/LiF/PEDOT : PSS/MEH-PPV : C60/C60/Al and Device 4 ITO/PEDOT : PSS/MEH-PPV : C60/C60/Al. Then we compared the current-voltage (I-V) characteristics of these devices and found that the insertion of a thin LiF layer between the ITO electrode and the PEDOT : PSS layer resulted in much improved device performance. The short-circuit current density (J(sc)) and fill factor (FF) of Device 1 were enhanced by 74% and 31%, respectively as compared to those of Device 2. The short-circuit current density (J(sc)) of Device 3 is about 1.4 times as large as that of Device 4. The increased solar cell performance mostly can be attributed to the fact that the hole transport to the anode can be effectively suppressed by a thin LiF layer, and the thin LiF layer between the ITO electrode and the PEDOT: PSS layer can form better interface properties. Hence, such change in structure of solar cells improves the performance of the organic solar cells effectively.

RESUMEN

ZnSe nanocrystals were synthesized in aqueous solution by using mercapto-acetate acid as stabilizer. Products were characterized by X-ray diffraction patterns (XRD) and X-ray photoelectron spectra (XPS). A surfactant was used to transfer the nanocrystals from the aqueous solution to organic solvent, so that ZnSe and MEH-PPV could be mixed sufficiently and were used as an emitting layer in a multilayered electroluminescence device: Glass/ITO/MEH-PPV : ZnSe /BCP/Alq3/LiF/Al. A comparison between absorption spectra and photoluminescence spectra of ZnSe nanocrystals and MEH-PPV thin film exhibits an effective energy transfer from ZnSe nanocrystals to MEH-PPV, which is one reason for the existing difference between photoluminescence spectrum and electroluminescence spectrum of MEH-PPV : ZnSe nanocomposite film. The recombination mechanism of the nanocomposite film under photoexcitation and electric injection was discussed respectively. The authors investigated the photo- and electroluminescence properties of the device, and found that the EL intensity of ZnSe nanocrystals increased with the applied voltages. The I-V characteristic of this device is similar to that of a classic diode.

RESUMEN

A new method for measuring time-resolved spectrum (TRS) is brought forward. Programming with assemble language controlled the micro-control-processor (AT89C51), and a kind of peripheral circuit constituted the drive circuit, which drived the stepping motor to run the monochromator. So the light of different kinds of expected wavelength could be obtained. The optical signal was transformed to electrical signal by optical-to-electrical transform with the help of photomultiplier tube (Hamamatsu 1P28). The electrical signal of spectrum data was transmitted to the oscillograph. Connecting the two serial interfaces of RS232 between the oscillograph and computer, the electrical signal of spectrum data could be transmitted to computer for programming to draw the attenuation curve and time-resolved spectrum (TRS) of the swatch. The method for measuring time-resolved spectrum (TRS) features parallel measurement in time scale but serial measurement in wavelength scale. Time-resolved spectrum (TRS) and integrated emission spectrum of Tb3+ in swatch Tb(o-BBA)3 phen were measured using this method. Compared with the real time-resolved spectrum (TRS). It was validated to be feasible, credible and convenient. The 3D spectra of fluorescence intensity-wavelength-time, and the integrated spectrum of the swatch Tb(o-BBA)3 phen are given.

RESUMEN

A new rare earth complex TbGd(BA)6(bipy)2 was synthesized, which was used as an emitting material in electroluminescence. By doping with poly-N-vinylcarbazole (PVK), the stability and conductivity of terbium complex were improved. The photoluminescence of PVK, terbium complex and their blend indicated that energy transfer from PVK to terbium complex occurred. In the present paper, single-, double- and multi-layer devices were fabricated. In the double-layer devices, holes and electrons were recombined at the interface of emitting layer (EML) and electron transporting layer (ETL). With increasing the thickness of Alq3, especially at highly electric field, carrier composite region transferred closely to ETL. However, in multi-layer devices, carrier composite region was restricted at the interface of emitting layer and holes blocking layer (HBL) due to high HOMO level of BCP. Enhancing electric field, emission from terbium complex was getting saturation gradually and weak emission from PVK was observed. From the optimized multi-layer device, bright and green emission from terbium complex was obtained with the highest EL brightness of the device of 213 cd x m(-2) at 13.5 V.

RESUMEN

The decay curves of the emission at different wavelength were measured. One nanosecond of transition lifetime of interband was obtained. The transient dynamics of InP nanoparticles was investigated by one color femtosecond pump-probe method at the wavelength of 800 nm. The experimental result shows that the saturation of exciton resonance results in photobleaching at 800 nm The decay process of the bleaching includes two components, i.e. the fast one from free carries scattering and the slow one from trapped carriers scattering. The nonlinear optical properties of InP nanoparticles were investigated by using femtosecond optical Kerr effect. The magnitude of chi3 for InP nanoparticles embedded in SiO2 sol-gel glass was calculated, and its origin was analyzed.

RESUMEN

Electroluminescent (EL) properties of the terbium complex [Tb(m-MBA)3 phen]2 x 2H2O doped PVK system were investigated. Two kinds of devices with the structures of ITO/PVK: Tb complex/PBD/LiF/Al and ITO/PVK: Tb complex: PBD/PBD/LiF/Al were fabricated. PBD emission appears in the EL spectra of ITO/PVK: Tb complex/PBD/LiF/Al in comparison with ITO/PVK: Tb complex: PBD/PBD/LiF/Al. The reason is that PBD acts as a hole blocking material in the emitting layer (PVK: Tb complex: PBD) and thus the combination of excitons mostly occur within this layer. The energy of terbium complex emission comes from two different ways, namely energy transfer and direct combination of carriers. By altering the doping weight ratio of PBD, a set of devices were fabricated with the configuration of ITO/PVK: Tb complex: PBD/PBD/LiF/Al. Both the efficiency and brightness of these devices decrease with the rising of the PBD doping weight ratios. The efficiency of the carriers trapping may decrease with the rising of PBD doping ratios, for PBD may block the hoping of hole or electron between the PVK chains, causing a decrease in the brightness and efficiency. The PBD doping ratios have little effect on the efficiency of Förester energy transfer based on our synthesis.

RESUMEN

Photoconductive properties of the composite devices made up of cadmium selenide nanocrystals and polymer poly[2-methoxy-5-(2'-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) were investigated. The photocurrent action spectrum for a nanocomposite device corresponded to the absorption of MEH-PPV and CdSe nanocrystals, indicating that the absorption of the CdSe nanocrystals and MEH-PPV contributed to the photocurrent. The photocurrent was attributed to the exciton dissociation and charge transfer between the interface of CdSe nanocrystals and MEH-PPV. The photocurrent action spectra of the nanocomposite device was wider than that of the pure MEH-PPV device, and the photocurrent was enhanced in comparison with the pure MEH-PPV device due to the introduction of CdSe nanocrystals.

RESUMEN

A new rare earth complex Tb(BSA)4 was synthesized and studied. Pure green and narrow band emission was generated from the device with structure ITO/PVK:Tb(BSA)4 /Alq3 /LiF/Al, where PVK was used to improve the film-formation and hole-transport property of the Tb(BSA)4. The absorption mechanism, and the photoluminescence and electroluminescence mechanisms are discussed. It has been proved that there exists energy transfer from PVK to Tb(BSA)4 and the mechanisms of photoluminescence and electroluminescence are different. The effect of different ratios of PVK on the device characteristics is also studied.

Asunto(s)

RESUMEN

Rare earth complex TbY(m-MBA)6 (phen)2.2H20 have been synthesized, which were used as emitting materials in electroluminescence. Single-layer devices and bilayer devices with Alq as electron transmission layer have been fabricated. The electroluminescent properties of the devices were studied. The electroluminescent mechanism of the devices was proposed by measuring and analyzing the emission and the excitation spectra of the emissive layer. Y3+ may play the role to promote the energy transfer from ligand to Tb3+ and the possible energy transfer process of the device was preliminarily discussed.

Asunto(s)

RESUMEN

Water-sol core/shell CdSe/CdS quantum dots (QDs) were synthesized in aqueous solution by using mercapto-acetate acid as stabilizer. The UV-Vis absorption and emission spectra were studied. The size of the SdSe-core was about 2 nm estimated by absorption edge and X-ray powder diffraction(XRD). The structure was also characterized by X-ray photoelectron spectroscopy(XPS). The intensity of luminescence of the quantum dots was greatly enhanced after the surface was modified with CdS shell. Red shift of the peak was shown in both the emission and absorption spectra.

Asunto(s)

RESUMEN

An organic photovoltaic(PV) cell, ITO/MEH-PPV/Alq3/LiF/Al, was fabricated. The MEH-PPV and Alq3 are the electron-acceptor and donor in the cell, respectively. The respond region matchs the adsorption of Alq3 film. Under UV light with 0.5 mW x cm(-2), the cell shows a short-circuit current of 2.4 microA x cm(-2), open-circuit voltage of 2.6 V, a fill factor of 0.71, and a power conversion efficiency of 0.9%. It was found that the PV cell indicates electroluminescence (EL) performance and could emit orange light at DC voltage. The maximum luminance is about 1 000 cd x cm(-2) at 15 V.

Asunto(s)

RESUMEN

In the present report, the authors studied the movement of pigment particles which decide the display status, enduced the equation of the motion and the expression of reflectivity, and estimated the value of the delay time. Combining the above theoretical conclusion with the experimental results, the authors discussed the feasibility of the passive matrix addressing of electrophoretic image displays, and provided good advice on how to acquire display devices of good quality.

Asunto(s)

RESUMEN

Excitation and photoluminescence (PL) spectra of the mixture terbium complex and PVK were investigated. The excitation spectrum of Tb complex dispersed PVK film is very similar to that of the pure PVK film, indicting that energy transfer occurs from PVK to Tb complex. For the overlap between the excitation spectrum of Tb complex dispersed PVK film and the PL spectrum of PVK film is very little, the ratio of occurrence for Förester energy transfer is very little. The emission of Tb3+ mainly comes from the excited ligand, which comes from the ligand capture of electron-hole pairs. In the electroluminescence (EL) spectra, the emission of PVK is completely restrained and only emission of Tb3+ is occured, which origins from the different mechanism in comparison with photoluminescence.

Asunto(s)