Fabrication And Electroluminescent Properties Of ZnO Nanocrystals/Si Heterostructures

ZnO is a third-generation semiconductor material that possesses superior optoelectronic characteristics(with direct wide bandgap of 3.37 eV and exciton binding energy of 60 meV).Herein,heterostructured light-emitting diodes(LEDs)based on ZnO NCs was prepared by sol-gel method.Electroluminescence(EL)performance of the devices was improved by introducing an electron blocking layer(EBL,i-NiO),a surface modification layer(aluminum doped ZnO,AZO)and rare earth ions(Er3+).The primary achievements are described and listed in detail in the following paragraphs.First of all,n-ZnO NCs/i-NiO/n-Si isotype heterojunction LEDs were fabricated by combining radio frequency magnetron sputtering with the spin-coating method.EL and time-resolved photoluminescence(TRPL)measurements displayed that the EL of the n-ZnONCs/i-NiO/n-Si diode gets brighter,almost as six times as that of the LEDs without i-NiO EBL,which is attributed to the higher hole injection efficiency induced by the i-NiO EBL.This work indicates that the i-NiO EBL could effectively improve the EL performance of the n-ZnO NCs/n-Si isotype heterojunction LEDs.Secondly,A strategy to realize ZnO-based near-white-light EL was proposed by utilizing and regulating the intrinsic defect-related emissions of ZnO NCs.The emission color of the n-ZnO NCs/n-Si isotype heterojunction LEDs was tuned toward near white by using an AZO spectral scissor,which can tailor the green light more severely,rather than the blue or red light.Moreover,quantum size effect was clearly observed in both the PL and EL spectra via the redshift of the near-band-edge UV emission of the ZnO NCs.At last,LEDs of ZnO NCs:Er3+/p-Si with Er3+doping concentrations of 0%,0.85%,and 2.5%was prepared by sol-gel method.PL and EL measurements indicate that the intensity of the Er3+related emission peaks due to the transitions from the 2H11/2,4S3/2 and 4F9/2 to 4I15/2 levels increases with increasing Er3+ concentration.When the Er3+doping concentration was 1.95%,both the PL and EL spectra displayed a distinct characteristic peak attributed to the Er3+ dopant,and a green LED with a CIE coordinate of(0.33,0.49)was obtained.