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Light Manipulation For Organic Electronics Using Bio-inspired Moth Eye Nanostructures

Posted on:2016-04-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:L ZhouFull Text:PDF
GTID:1108330464955028Subject:Condensed matter physics
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Organic optoelectronic devices, including organic light-emitting devices(OLEDs) and organic solar cells(OSCs) are gaining increasing importance in various applications including full-color display panels, solid lighting, fascinating flexibility and renewable energy application. However, further improvement in efficiency remains a daunting challenge due to limited light extraction or trapping in conventional planar device architectures. It is an efficient method to improve efficiency by introducing micro/nano structures into OLEDs and OSCs following the amazing progress of modern optical nanofabrication technologies. In this thesis, to achieve advanced light management with wavelength independence and wide viewing angle, the biomemetic moth eye nanostructures have been fabricated and successfully incorporated into OLEDs and OSCs by soft nanoimprinting technology, yielding the striking efficiencies enhancement. The major work can be summarized in six parts as follows:In chapter one, the development history, working principle, device architectures as well as the factors related to the efficiency of OLEDs and OSCs are summarized. The status and the limitation of previously reported light management methods are discussed. Then, the subjects and importance of this thesis are proposed.In chapter two, quasi-periodic moth eye nanostrutures are fabricated by siliver mirror rection combined with the etching technique. Then, the parameters related to the profile of moth eye nanostructures are studied in details. Finally, positive and negative perfluoropolyethers molds are fabricated by soft nanoimprinting lithography and characterized.In chapter three, the procedures involved in fabricating monochromatic OLEDs IV based on ITO glass substrate with moth eye nanostructures are discussed. Nanostructured phosphorescent green OLEDs with stacked single, double, triple emission units are fabricated, and the corresponding electrical, spectral properties are characterized. Furthermore, the nanostructured phosphorescent red and blue OLEDs are alse fabricated for a comparison. Green OLEDs with dual-side bio-inspired moth eye nanostructures and single emission layer yields external quantum efficiency(EQE) of 41.1% and enhancement of 246% in light-outcoupling efficiency(@1000 cd m2). Particularly, the nanostructured green OLEDs with a tandem structure of triple emission units is over 2 times that of a conventional device, resulting in drastic increase in current efficiency to 366 cd A-1without introducing spectral distortion and directionality spectral distortion and directionality. The instantaneous energy intensity distributions are calculated based on Finite Difference Time Domain(FDTD) method.In chapter four, regular and inverted moth eye nanostructures are designed and fabricated. The corresponding optical transmittance, capacity against scrubbing and self-cleaning features are extensively investigated. As a result, white OLEDs with inverted moth eye nanostructures were fabricated, the power efficiency are raised from 17.53 lm W-1 to 43.50 lm W-1(maxmimum) with enhancement factor of 2.48.In chapter five, the fabrication procedures, morphology, optical transmittance and electrical characteristics of the plastic embedded Ag networks(PEANs) are studied in details. Highly power-efficient large-area green and white OLEDs have been fabricated on PEANs, yeliding power efficiency of 123.5 lm W-1 and 106.0 lm W-1(@1000 cd m-2) for green and white OLEDs respectively, which is among the highest values ever reported for flexible OLEDs in the literature. Lastly, far field distributions, dispersion diagrams and energy flow distributions are simulated by comprehensively utilizing three dimentional Monte Carlo ray tracing method, FDTD method and rigorous coupled wave analysis(RCWA).In chapter six, OSCs with PTB7:PC71BM active layer based on nanostructured Zn O electron layer coated on ITO glass substrated have been fabricated. Similarly, the light in-coupling efficiency of OSCs is increased 20%, yielding an enhanced power conversion efficiency of 9.33%.Finally, the subjects of this study were summarized, and future developments of the related areas are discussed.
Keywords/Search Tags:Nanoimprinting, moth eye, nanostructure, light management, OLED, OSC
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