Schematic illustrations of MAPbBr3 with and without APMs. a) Schematic of bromide ion vacancies on the surface of MAPbBr3 without APMs. Device performance of PeLEDs and SEM images on the top surface of MAPbBr3 with and without APMs. a) Current density versus voltage (J-V) characteristics.
Introduction
Organic Optoelectronic Devices
- Organic Light-Emitting Diodes (OLEDs)
- Organic Solar Cells (OSCs)
The internal quantum efficiency is the ratio of the number of photons generated inside OLEDs per second to the number of charges passing through OLEDs per second. The external quantum efficiency is the number of photons escaping from OLEDs per second to the number of charges passing through OLEDs per second.
Organic-Inorganic Hybrid Optoelectronic Devices
- Conventional Structure
- Inverted Structure
Generally, zinc oxide (ZnO), titanium oxide (TiOx) and tin oxide (SnO2) are used as electron transport layers, and molybdenum oxide (MoO3), nickel oxide (NiOx) and vanadium oxide (V2O5) are introduced as a hole transport. layers in the inversely structured optoelectronic devices. The reverse-structured optoelectronic devices exhibit excellent device stability by using air-stable metal oxides as the charge transport layer and high-work function air-stable metal as the cathode15-18.
Interfacial Engineering
- Energy Level Control
- Defect Control
- Compatibility Control
Schemes of changing the energy level with and without an interphase dipole layer are shown in Figure 1.14. A summary of iPSC device performance with and without the CPU layer is shown in Table 1.3.
Organic-Inorganic Hybrid Perovskite Devices
- Perovskite Light-Emitting Diodes
- Perovskite Solar Cells
Reducing the size of the perovskite grains increases the probability of bimolecular recombination by spatially limiting the charges within the small grains, as shown in figure 1.3048. Perovskite solar cells were demonstrated using methylammonium lead halide perovskites (CH3NH3PbX3) as light absorbers in dye-sensitized liquid electrolyte solar cells by Miyasaka in 2009, as shown in Figure 1.3151.
R.; Inganas, O., Correlation between oxidation potential and open circuit voltage of composite solar cells based on mixtures of polythiophenes/fullerene derivative. J.; Coronado, E.; Repetto, D.; Sessolo, M., Air-stable hybrid organic-inorganic light-emitting diodes using ZnO as the cathode.
Combination effect of polar solvent treatment on ZnO and polyfluorene-based
- Research background
- Experimental
- Results and discussion
- Conclusion
- Reference
Combination effect of polar solvent treatment on ZnO and polyfluorene-based polymer blends for highly efficient blue-based hybrid. The IPLEDs with polar co-solvent treatment on ZnO were optimized by different volume concentrations and the optimized volume concentration of EA in 2-ME is 5.00 vol. The EL spectra of the IPLEDs with polar cosolvent treatment do not change compared to the EL spectrum of reference IPLED and EL spectra of optimized IPLED (FTO/ZnO/2-ME+EA (5.00 vol.
We have demonstrated a highly efficient blue-based hybrid organic-inorganic IPLED with 2-ME+EA polar solvent treatment on ZnO layer and introduction of a small amount of TFB as a hole trap in F8 emitting polymer.
Amine-based interfacial molecules for inverted polymer-based optoelectronic
Research background
In this paper, we present a novel interface engineering method by introducing a series of amine-based interfacial molecules (AIM) containing 2 to 6 amine groups (2N to 6N) for high-efficiency iPLED and iOSC devices. Our method ensures simple and efficient processing and effective tunability of the energy level at the interface between the ZnO and the active layer, depending on the number of amine groups. We investigate the effect of the number of amine groups of one solvent molecule on the tunability of the energy barrier by recording the total number of amine groups in AIM solutions.
Different concentrations of amine groups are used in iPLEDs (0.30 M) and iOSCs (0.06 M) for optimized device performance.
Experimental
They cannot easily control the desired energy levels at the interface between ZnO and the active layer depending on the device configuration such as iPLED and iOSC. In general, higher device performance in iPLEDs requires a thicker interlayer because a thicker interlayer effectively blocks hole carriers and reduces exciton damping at the interface between ZnO and the emissive layer 27,31 . However, a thinner interfacial layer is more suitable for efficient charge extraction from the active layer in ZnO in iOSCs32.
For iPLEDs, the J-V-L characteristics and device performances were measured using a Konica Minolta spectroradiometer (CS-2000) with Keithley 2400 source meter, respectively.
Results and discussion
To understand the possible origin of WF reduction depending on the number of amine groups on the surface of the ZnO layer, a quantitative X-ray photoelectron spectroscopy (XPS) analysis was performed (Figure 3.6b). The total number of amine groups in the AIM solution was determined as shown in Table S2. The total intensities of the N1s and N-Zn peaks increased along with the number of amine groups in AIM.
However, as the number of amine groups in AIM increases, the number of unadsorbed nitrogen can also increase, as shown in Figure 3.13.
Conclusion
P; Li, G.; Yang, Y., Metal oxide nanoparticles as electron transport layer in high-performance and stable inverted polymer solar cells. 25 Kang, H.; Hong, S.; Lee, J.; Lee, K., Electrostatically self-assembled non-conjugated polyelectrolytes as an ideal boundary layer for inverted polymer solar cells. K; Kim, Y., 8.9% single-stack inverted polymer solar cells with electron-rich polymer nanolayer-modified inorganic electron-collecting buffer layers.
J.; Murase, S.; Moriarty, T.; Emery, K.; Li, G.; Yang, Y., Tandem polymer solar cells with a spectrally tailored low-bandgap polymer.
Conjugated polyelectrolytes bearing various ion densities: spontaneous dipole
Research background
Conjugated Polyelectrolytes Carrying Different Ion Densities: Spontaneous Dipole Generation, Polym.-Induced Dipole Stretching, and Control of the Interfacial Energy Barrier for.
Experimental
ZnO was deposited on the cleaned ITO substrate by the spin-coating method and baked at 400 °C for 20 min. The J-V-L characteristics and device efficiency were obtained using a Keithley 2400 source meter with a Konica Minolta spectroradiometer (CS-2000). Exciton lifetimes of SY films with and without CPE films were determined using time-correlated photon counting (TCSPC) setup (Fluotime 300, PicoQuant).
PL spectra of SY films with and without CPE films were measured with a Cary Eclipse spectrofluorometer (Edinburgh Instruments, Ltd.).
Results and discussion
Moreover, the L and efficiency of the iPLEDs with MPBs gradually increase with increasing MPB ion density (Figure 4.11a,b). Instead, we measured the time responses of the J and L of the iPLEDs with 10-nm-thick MPBs at a constant voltage of 6 V for 3 min. The device performances of the iPSCs with MPBs were higher than those without MPBs due to spontaneous negative dipole formation (even before poling).
To elucidate the effect of poles on the performance of iPSCs, devices with 8 nm thick CPE layers were also prepared.
Conclusion
Regarding the interface energy level adjustment mechanism, the permanent spontaneous dipole model is suitable when the CPE film is thin (2 nm), whereas internal field redistribution by ion migration applies when the CPE film is thick (10 nm). The spontaneous polarization (with negative dipoles) was enhanced with increasing CPE ion density (MPB2 → MPB6), thereby increasing the VOC and J for ZnO/CPE/SY. The results of this study show that the tuning of the interfacial energy level and charge injection/extraction can be finely modulated by using this series of CPEs carrying different ion densities and additional electrical poling for iPLED and iPSC optimization.
L.; Cao, W.; Yang, W.; Cao, Y., Highly efficient, environmentally friendly electroluminescent polymers with high work function stable metal as cathode: Conjugated green and yellow emitting polyfluorene polyelectrolytes and their neutral precursors. B.; Cao, W.; Yang, W.; Cao, Y., Synthesis and characterization of polyfluorene electrolytes as green and red light-emitting layers for high-efficiency PLEDs. H.; Wang, L.; Zhang, K.; Guan, X.; Huang, F., Conjugated zwitterionic polyelectrolytes and their neutral precursor as electron injection layer for high performance polymer light emitting diodes.
J.; Cao, Y., Simultaneous enhancement of open-circuit voltage, short-circuit current density and fill factor in polymer solar cells.
Amine-based passivating materials for enhanced optical properties and
Research Background
Here we present an effective method to passivate the defect sites in methylammonium lead tribromide (MAPbBr3) by introducing amine-based passivating materials (APMs) to enable the fabrication of highly efficient PeLEDs with excellent stability. To investigate the effect of the molecular size of the APMs on the passivation of defects in the perovskite crystals, we used two different APMs, namely branched polyethyleneimine (PEI) and ethylenediamine (EDA). We observed that perovskite films containing APMs exhibited enhanced photoluminescence (PL) intensities, long PL lifetimes, and reduced PL blinking due to the significant suppression of nonradiative recombination.
Furthermore, the APM treatment significantly suppressed electrode corrosion by inhibiting ion migration from the perovskite layer to the metal electrode, thereby improving device stability.
Experimental
Decay curve deconvolution was performed using fitting software (FluoFit, PicoQuant) to derive the time constant associated with each exponential decay curve. Confocal PL images of the perovskite films were acquired using an LSM 780 NLO laser scanning confocal microscope (Carl Zeiss) with a 100x oil immersion objective ( Plan-APO, NA = 1.46). SEM images of the perovskite films were obtained using a scanning electron microscope (Nanonova 230, FEI) operated at an accelerating voltage of 10 kV.
The XRD patterns of the perovskite films were measured with an X-ray diffractometer (D8 Advance, Bruker) equipped with a Cu-K Å radiation source.
Results and Discussion
The normalized PL spectra of the MAPbBr3 with APMs are slightly blue-shifted compared to those of MAPbBr3 without APMs (Figure 5.5), and they show sharp band-edge emission due to the passivation of shallow trapping levels44. To investigate the passivation effect of the studied APMs on the PL blinking of MAPbBr3, we obtained confocal PL images and PL intensity trajectories of the MAPbBr3 material with and without APMs over time (Figure 5.8). The MAPbBr3 without APMs showed a significant increase in PL intensity compared to that of the MAPbBr3 materials with APMs, indicating that the MAPbBr3.
Moreover, the higher initial PL intensity of APM-passivated MAPbBr3 compared to photo-stabilized MAPbBr3 without APM demonstrates the effective passivation ability of APM.
Conclusion
Corrosion of Ag on MAPbBr3 and operational stability of PeLEDs with and without APMs. a) Photographs of Ag on MAPbBr3 material with and without APMs under ambient conditions over time. Moreover, APM treatment completely prevents electrode corrosion by inhibiting ion migration from the perovskite layer to the metal electrode, leading to improved device stability. Consequently, this method allowed us to fabricate optimized PeLEDs with EDA that exhibited a remarkable maximum luminance of 22,800 cd m-2 and EQE of 6.2%, with excellent device stability.
We believe that this improvement in device efficiency and long-term stability of PeLEDs with simultaneous suppression of PL switching can contribute to the commercialization of PeLEDs.
26 Seth, S.; Mondal, N.; Patra, S.; Samanta, A., Fluorescence Blinking and Photoactivation of All-Inorganic CsPbBr3 and CsPbBr2I Perovskite Nanocrystals. B.; Edvinsson, T.; Boschloo, G., Frustrated Lewis Pair Mediated Recrystallization of CH3NH3PbI3 for Improved Optoelectronic Quality and High Voltage Planar Perovskite Solar Cells. M.; Zhao, N., Phenylalkylamine passivation of organohalide perovskites enabling highly efficient and air-stable photovoltaic cells.
L.; Tena-Zaera, R., Layerless electron transport solar cells based on perovskite-fullerene blend films with improved performance and stability.
Growth of Nano-Sized Single Crystals for Efficient Perovskite Light-Emitting
Research Background
Experimental
After a 30-s delay, 80 μl of the PMA/CB antisolvent solution was dropped and spin-cast onto the precursor film. SEM images of the MAPbBr3 films on the glass/PEDOT:PSS substrates were obtained using a Nanonova 230 FEI SEM with an accelerating voltage of 10 kV. The XRD patterns of the glass/PEDOT:PSS/perovskite films were measured using a D8 Advance diffractometer (Bruker) equipped with a Cu K radiation source Å.
The PLQY of MAPbBr3 films on glass substrate with and without PMA treatment was obtained by the integrating sphere method.
Results and Discussion
Schematic illustrations of the MAPbBr3 film formation with and without PMA in the antisolvent at different temperatures. The morphologies of the MAPbBr3 films prepared with different concentrations of PMA at different temperatures were observed using SEM (Figure 6.3a). Moreover, the morphologies of the MAPbBr3 films prepared with different PMA concentrations at a low temperature (10~15°C) were also observed (Figure 6.5).
SEM images of the MAPbBr3 films prepared without PMA (Ref.) and with different PMA concentrations at low temperatures.
Conclusion
25 Tachikawa, T.; Karimata, I.; Kobori, Y., Surface charge trapping in organolead halide perovskites probed by single-particle photoluminescence imaging.
Summary
Acknowledgements (감사의 글)
