Building blocks for gas-phase-processed perovskite LED
| Autor: | Simkus, Gintautas |
|---|---|
| Přispěvatelé: | Heuken, Michael, Waser, Rainer |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2021). doi:10.18154/RWTH-2021-04785 = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021 |
| DOI: | 10.18154/rwth-2021-04785 |
| Popis: | Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2021). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021 The halide perovskites CH3NH3PbX3 and CsBrX3 (X = I, Br, Cl) have recently emerged as promising emitter materials for optoelectronics owing to their readily tunable bandgap, high photoluminescence quantum yield, and ultra-narrow emission spectra (full-width at half maximum (FWHM) ranging from 12 nm to 40 nm). The use of these emitters in LED structures allows for high emission intensity in a wide range of spectral colors, perfectly suited for next-generation displays. However, the most efficient perovskite LED (PeLED) with external quantum efficiencies (EQE) approaching 20 % rely on solution-processed perovskite films, restricting their compatibility to established state-of-the-art display patterning technologies. Besides, limited scalability and the need for toxic solvents hamper a high-volume PeLED production on large-area substrates. Conversely, chemical vapor deposition (CVD) as solvent-free thin-film fabrication technology provides precise process control and improved scalability. Thus, CVD is an attractive choice to overcome hurdles related to the manufacture of PeLED-based displays. However, due to a lack of available CVD tools, knowledge on perovskite crystal growth and film formation mechanisms remains limited.To improve the understanding of chemical and physical processes governing PeLED performance, the properties of solution-processed CsPbBr3 films on different hole transport layers (HTL) were investigated. It was shown that PTAA (ploy(triaryl amine)) acts as a multifunctional layer demonstrating hole-transport, electron-blocking, and defect passivation capabilities. The outstanding performance of PTAA compared to the conventionally used PEDOT:PSS (poly(3,4-ethylendioxytiophene) polystyrene sulfonate) was confirmed in a simplified PeLED architecture based on undoped CsPbBr3 films, showing a tenfold higher EQE of 3.3%. Besides, the superior chemical and thermal stability of PTAA was identified as the main reason for an improved operational PeLED lifetime from 15 hours to 39 hours at a luminance of 100 cd/m2.PTAA-coated substrates were also utilized to develop CVD processes for CH3NH3PbBr3 and CsPbBr3 films and to improve the general understanding of perovskite crystallization kinetics. Fully vapor-deposited perovskite films were fabricated in a custom-built CVD tool based on a showerhead and hot-wall reactor design. The sublimed precursor molecules were homogeneously distributed in an N2 carrier gas stream by a static forced-mixing unit and the showerhead concept. This, in combination with precise flow control, enabled a uniform deposition of perovskite films with improved process control and reduced parasitic material deposition. It was demonstrated that the morphology and optical properties of perovskite films can be fine-tuned by adjusting growth temperatures and deposition rates. Highly emissive and dense CH3NH3PbBr3 films were obtained by growing them at CH3NH3Br-rich conditions and low substrate temperatures (60 °C). The morphological and optical properties were determined to deteriorate for perovskites grown at CH3NH3Br-deficient conditions and higher substrate temperatures (> 100 °C). Ultra-narrow EL spectra (FWHM of 20 nm) obtained from PeLED based on CVD-CsPbBr3 films proved that CVD technology is capable of producing high-quality perovskite films for LED application. This paves the way for further systematic studies on novel perovskite/HTL interfaces and PeLED. Published by RWTH Aachen University, Aachen |
| Databáze: | OpenAIRE |
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