Ca2BO3Cl:Ce3+,Ca2BO3Cl:Tb3+,and Ca2BO3Cl:Ce3+,Tb3+ phosphors are synthesized by a high temperature solid-state reaction.The emission intensity of Ce3+ or Tb3+ in Ca2BO3Cl is influenced by the Ce3+ or Tb3+ doping content,and the optimum concentrations of Ce3+ and Tb3+ are 0.03 mol and 0.05 mol,respectively.The concentration quenching effect of Ce3+ or Tb3+ in Ca2BO3Cl occurs,and the concentration quenching mechanism is d-d interaction for either Ce3+ or Tb3+.The Ca2BO3Cl:Ce3+,Tb3+ can produce colour emission from blue to green by properly tuning the relative ratio between Ce3+ and Tb3+,and the emission intensity of Tb3+ in Ca2BO3Cl can be enhanced by the energy transfer from Ce3+ to Tb3+.The results indicate that Ca2BO3Cl:Ce3+,Tb3+ may be a promising double emission phosphor for UV-based white light emitting diodes.
The contact effect on the performances of organic thin film transistors is studied here.A C 60 ultrathin layer is inserted between Al source-drain electrode and pentacene to reduce the contact resistance.By a 3 nm C 60 modification,the injection barrier is lowered and the contact resistance is reduced.Thus,the field-effect mobility increases from 0.12 to 0.52 cm 2 /(V·s).It means that inserting a C 60 ultra thin layer is a good method to improve the organic thin film transistor (OTFT) performance.The output curve is simulated by using a charge drift model.Considering the contact effect,the field effect mobility is improved to 1.15 cm 2 /(V·s).It indicates that further reducing the contact resistance of OTFTs should be carried out.
