Zhang Yanfei

Enhanced performance in organic photovoltaic devices with a KMnO4 solution treated indium tin oxide anode modification

The properties of poly(3-hexylthiophene):(6,6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM) organic photovoltaic devices (OPVs) with an indium tin oxide (ITO) anode treated by a KMnO4 solution are investigated. The optimized KMnO4 solution has a concentration of 50 mg/L, and ITO is treated for 15 min. The modification of ITO anode results in an enhancement of the power conversion efficiency (PCE) of the device, which is responsible for the increase of the photocurrent. The performance enhancement is attributed to the work function modification of the ITO substrate through the strong oxygenation of KMnO4, and then the charge collection efficiency is improved.

The Metal Intermediate Electrode: A Method to Improve the Current Efficiency of a Tandem Organic Light-Emitting Diode

We prepare a tandem (OLED) with two independent units and three electrodes. One of the units consists of ITO/TPD/Alq3:DCJTB (5%)/LiF/Al/Au, and the other is Al/Au/TPD/Alq3/LiF/Al. Two units sharing one transparent intermediate electrode Al/Au, together constitute the entire device. With the same current density, the voltage of the entire device is approximately equal to the sum of two units. The current efficiency of the entire device is several times higher than the sum up of two components. Without directly contacting an external power supply, the bi-metal intermediate electrode has the ability to produce electrons and holes for two adjacent emitting units, respectively. This kind of tandem device is characterized by controllable emission color and higher current efficiency than its two components added up.

The effects of radiation damage on power VDMOS devices with composite SiO2—Si3N4 films

Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor (VDMOS) devices with composite SiO2—Si3N4 film gates are investigated. The relationships among the important electrical parameters of the samples with different thickness SiO2—Si3N4 films, such as threshold voltage, breakdown voltage, and on-state resistance in accumulated dose, are discussed. The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose. However, the relationships between the threshold voltages of the samples and the accumulated dose are more complex, and not only positively drift, but also negatively drift. At the end of the total dose experiment, we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies. We find that the samples with appropriate thickness ratio SiO2—Si3N4 films have a good radiation-hardening ability. This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2—Si3N4 films.

Deposition of Cu seed layer film by supercritical fluid deposition for advanced interconnects

The deposition of a Cu seed layer film is investigated by supercritical fluid deposition (SCFD) using H2 as a reducing agent for Bis(2,2,6,6-tetramethyl-3,5- heptanedionato) copper in supercritical CO2 (scCO2). The effects of deposition temperature, precursor, and H2 concentration are investigated to optimize Cu deposition. Continuous metallic Cu films are deposited on Ru substrates at 190 ?C when a 0.002 mol/L Cu precursor is introduced with 0.75 mol/L H2. A Cu precursor concentration higher than 0.002 mol/L is found to have negative effects on the surface qualities of Cu films. For a H2 concentration above 0.56 mol/L, the root-mean-square (RMS) roughness of a Cu film decreases as the H2 concentration increases. Finally, a 20-nm thick Cu film with a smooth surface, which is required as a seed layer in advanced interconnects, is successfully deposited at a high H2 concentration (0.75 mol/L).

The Formation of Exciplex and Improved Turn-on Voltage in a Hybrid Organic-Inorganic Light-Emitting Diode

In order to take advantage of organic and inorganic materials, we chose the polymer MEH-PPV as the luminous layer and ZnS as the electron transporting layer to prepare hybrid organic-inorganic light-emitting diodes (HOILEDs): ITO/MEH-PPV(~70 nm)/ZnS(20 nm)/Al by thermal evaporation and spin coating. Compared with the single-layer device ITO/MEH-PPV(~70 nm)/Al, spectral broadening and a slightly red shift are observed. Compared with the pure organic device ITO/MEH-PPV(~70 nm)/BCP (20 nm)/Al and combined with the energy level structure diagram, it is concluded that the spectral broadening and red shift are due to the exciplex luminescence at the interface between MEH-PPV and ZnS or BCP. In addition, the hybrid inorganic-organic device shows a lower turn-on voltage, but the current efficiency is lower than that of the pure organic device with the same structure.