Study On Cascade Host-guest System Of Laser Dyes And Application In Organic Lasing

Organic semiconductor laser diodes have attracted much attention in recentyears owing to their special characteristics with the flexibility of organic materialsand easy processing merits and potential applications in modern display technologyand integrated optics. However, lasing material with high lasing threshold is oflong-standing interest in the field of organic lasing. For the organic electronics, thestudy of doped organic emissive materials has become an effective way to lower theturn-on voltage and improve the luminescence.Based on the analysis of organic materials and lasing with host-guest system,this dissertation mainly analyzes the luminescent characteristics and optical pumpingproperties for doped system with the deep blue organic laser dye BN1. Byjudiciously employing the red organic laser dye DCJTB and green laser dye DSB incombination with BN1, this work mainly focuses on F rster energy transfer in thedoped system. Based on the F rster energy transfer theory, we fabricated theco-doped organic light-emitting diodes (OLEDs) and investigated the effect of theenergy transfer mechanism on device performance. The main results of thedissertation include the following three aspects:The thesis firstly investigated the light-emitting properties of the pure film ofdeep blue laser dye BN1, and explored the lasing characteristics through theemission spectrum. From the analysis on BN1non-doped film under opticalpumping condition, the thesis obtained the relationship between spectral intensity,half-wave width and excitation intensity, and confirmed that the optical pump energydensity threshold of BN1material was4.4μJ/cm2. Meanwhile, we introduced smallmolecule material CBP as the host, and investigated the amplified spontaneousemission characteristics of the doped film CBP:3%BN1under the optical pumping.From the research, we verify the doped film has a7.0μJ/cm2threshold. The thesisalso studied energy transfer theory of the doped film with a low threshold. Secondly, by additionally introducing green organic laser dye DSB and redorganic laser dye DCJTB besides BN1, the thesis discussed the effect of overlappingareas between absorption and emission spectra of three materials on energy transferefficiency, masterly leading to the research of doped system. We prepared laserdye-doped organic film by spin coating, and focused on F rster energy transfer ofthe doped system. For the single-doped film of BN1:DCJTB, BN1:DSB andDSB:DCJTB, it is observed that the emission intensity of the host material increasedwith the increasing of the guest dye-doped concentration, indicating that effectiveenergy transfer occurs in doped film. However, the largest doped concentration doesnot accompany with the highest energy transfer efficiency due to the concentrationquench. For double-doped film of BN1:DSB:DCJTB, the excitation energy of BN1molecule can be transmitted not only directly, but through DSB as medium toDCJTB. And the use of DSB as an intermediate transfer member into BN1:DCJTBdoped system can efficiently reduce the doping concentration, lower the excitonconcentration quench. The cascade energy transfer mechanism can apart the film’semission spectrum and major absorption spectrum, reduce the absorption loss ofmaterials, consequently achieve a highly efficient light-emitting and improve theefficiency of energy transfer.Finally, to further study the effect of cascade energy transfer of doped systemon the luminescent properties, we fabricated the co-doped OLEDs with the structureof ITO/HI02/NPB/BN1:DSB:DCJTB/TPBi/LiF/Al. In combination with the analysison the spectra of double-doped devices, the results showed that energy transferplayed an important role rather than carrier trap. From the analysis on the dopeddevice, we obtained the result that efficiency drop with the increase of red-dyedoping concentration reduced by the concentration quenching in dye molecules andthe poor quantum yield.