Studies Of The Optical Process And Its Manipulating Methods In Organic Optoelectronic Devices

Organic electronics is one of the most attractive fields in research and development.Among various organic electronic devices,the external quantum efficiency of organic light-emitting diodes(OLEDs)are limited by the light out-coupling efficiency,and the electrical-pumped organic laser is still a dream due to many challenges.Therefore,from the perspective of the optical process and its manipulating method,both theoretical and experimental studies were carried out in this thesis to improve the out-coupling efficiency of OLEDs and develop suitable conductive distributed Bragg reflector(DBR)to construct the resonant cavity for the electrical-pumped organic laser.Among all of our researches,the optical theoretical analyzations were based on the finite difference time domain method.The specific researches and findings are as follows:1.A nano-honeycomb structured OLED was demonstrated through the monolayer colloidal crystal formed by the self-organized polystyrene spheres and micro-sphere lithography technology.The comparison of planar and nano-honeycomb structured OLEDs was carried out both theoretically and experimentally.It was proved that the nano-honeycomb structure can improve the external quantum efficiency of OLEDs via extracting the trapped energy of the waveguide mode and the surface plasma-polariton mode inside the planar OLEDs.2.The light extraction technology based on the nano-honeycomb structure was further improved by developing a nano-honeycomb structured conductive ITO substrate.This nano-structured ITO substrate was fabricated by chemical etching using the ordered perforated Si O₂ film as the mask,which was made from the monolayer colloidal crystal of polystyrene spheres and tetraethyl orthosilicate.The nano-structured ITO substrate can be a universal substrate applied in organic optoelectronic devices(such as OLEDs and solar cells)and it did help a lot to improve the efficiency of OLEDs.3.An organic-inorganic hybrid conductive DBR made of Mo O₃ and organic semiconductors was realized via the thermal evaporation deposition technique.After deep research and various optimization,high reflectivity and high conductivity were achieved in the hybrid conductive DBR.As it has good processing compatibility,the hybrid conductive DBR can be used to construct the organic electrical-pumped vertical-cavity surface-emitting laser(VCSEL)combined with OLEDs.4.To further improve the conductivity of the DBR,lead halide materials were investigated.Pb I₂ is found to be a good candidate as the high refractive index part in the DBR due to its good charge mobility,high refractive index and low melting point.The conductive DBR based on Pb I₂ with good performance was achieved.Combining with this new DBR with the OLEDs,the VCSEL like optoelectronic devices were demonstrated with very narrow electro-luminescent spectrum.5.Perovskite light-emitting diodes(LEDs)based on the organometallic halide material(CH₃NH₃Pb Br₃)were investigated.Through changing the fabrication process and the doping technique,some basic understandings of the properties of the organometallic halide material and the working mechanism of perovskite LEDs have been achieved.