Various infra-red and planar chiral metamaterials were fabricated using the modified Nanospherical-Lens Lithography. By replacing the light source with a hand-held ultraviolet lamp, its asymmetric ...light emission pattern produces the elliptical-shaped photoresist holes after passing through the spheres. The long axis of the ellipse is parallel to the lamp direction. The fabricated ellipse arrays exhibit localized surface plasmon resonance in mid-infra-red and are ideal platforms for surface enhanced infra-red absorption (SEIRA). We also demonstrate a way to design and fabricate complicated patterns by tuning parameters in each exposure step. This method is both high-throughput and low-cost, which is a powerful tool for future infra-red metamaterials applications.
Herein, the aspects of ion migration in polycrystalline CH3NH3PbBr3 thin film and their phenomenal influences on the output performance of perovskite light‐emitting diodes (PeLEDs) are reported. The ...physical insight of bias‐induced migration of mobile ions in the perovskite active layer effectuating the observed non‐linearity in the increased magnitude of electroluminescence (EL) and luminous efficiency (LE) as a function of current density for PeLEDs is directly evidenced using the capacitance spectroscopy. Adding the zwitterion molecule, Choline chloride (Ch.Cl), in CH3NH3PbBr3 precursor solution for preparing polycrystalline perovskite film effectively passivates the charged defects, either positively or negatively, in organic‐inorganic halide perovskite and most importantly interferes the migration of ions crossing the grains in PeLEDs as verified by the higher calculated magnitude of the activation energy for the migration of mobile ions. As a result, the Ch.Cl‐additive devices exhibit the rather stable EL and LE magnitude under the electric bias. EL magnitude increases linearly as a function of current density, revealing the epitome of output characteristics for decent light‐emitting diodes. To suppress the influence of the migrating ions on operating PeLEDs is a key issue before it is stepped further to advance the efficiencies and the operational stabilities of perovskite devices.
The external electric bias in operating CH3NH3PbBr3 perovskite light‐emitting diodes (PeLEDs) drives the migration of mobile ions and causes the bias‐induced enhancement of luminance. The studies clearly reveal the fundamental aspects to retard the migrating ions in operating PeLEDs, which would markedly advance the efficiencies and the operational stabilities of perovskite devices in future.
With the rapid progress in deposition techniques for hybrid organic-inorganic perovskite (HOIP) thin films, this new class of photovoltaic (PV) technology has achieved material quality and power ...conversion efficiency comparable to those established technologies. Among the various techniques for HOIP thin films preparation, vapor based deposition technique is considered as a promising alternative process to substitute solution spin-coating method for large-area or scale-up preparation. This technique provides some unique benefits for high-quality perovskite crystallization, which are discussed in this research update.
We introduce the use of low temperature sputtered NiOx thin film, which substitutes the PEDOT–PSS and solution-processed NiOx as an effective electron blocking layer for mesoscopic NiO/CH3NH3PbI3 ...perovskite solar cells. The influences of film thickness and oxygen doping on the photovoltaic performances are scrutinized. The cell efficiency has been improved from 9.5 to 10.7% for devices using NiOx fabricated under pure argon atmosphere. With adequate doping under 10% oxygen flow ratio, we achieved power conversion efficiency of 11.6%. The procedure is large area scalable and has the advantage for cost-effective perovskite-based photovoltaics.
Hybrid lead halide perovskites continue to attract interest for use in optoelectronic devices such as solar cells and light-emitting diodes. Although challenging, the replacement of toxic lead in ...these systems is an active field of research. Recently, the use of trivalent metal cations (Bi3+ and Sb3+) that form defect perovskites A3B2X9 has received great attention for the development of solar cells, but their light-emissive properties have not previously been studied. Herein, an all-inorganic antimony-based two-dimensional perovskite, Cs3Sb2I9, was synthesized using the solution process. Vapor–anion-exchange method was employed to change the structural composition from Cs3Sb2I9 to Cs3Sb2Br9 or Cs3Sb2Cl9 by treating CsI/SbI3 spin-coated films with SbBr3 or SbCl3, respectively. This novel method facilitates the fabrication of Cs3Sb2Br9 or Cs3Sb2Cl9 through solution processing without the need of using poorly soluble precursors (e.g., CsCl and CsBr). We go on to demonstrate electroluminescence from a device employing Cs3Sb2I9 emitter sandwiched between ITO/PEDOT:PSS and TPBi/LiF/Al as the hole and electron injection electrodes, respectively. A visible–infrared radiance of 0.012 W·Sr–1·m–2 was measured at 6 V when Cs3Sb2I9 was the active emitter layer. These proof-of-principle devices suggest a viable path toward low-dimensional, lead-free A3B2X9 perovskite optoelectronics.
The role of poly(ethylene oxide) polymer is investigated as an effective buffer with Al electrodes to markedly improve the electrode interface and enhance the open‐circuit voltage (VOC) and the power ...conversion efficiency (PCE, η) of poly(3‐hexylthiophene) (P3HT):6,6‐phenyl C61‐butyric acid methyl ester (PCBM)‐based bulk‐heterojunction (BHJ) solar cells. A unique process is developed by thermally co‐evaporating the poly(ethylene glycol) dimethyl ether (PEGDE, Mn ca. 2000) polymer with Al metal simultaneously at different ratios in vacuum (10−6 Torr) to prepare the electrode buffers. The instant formation of a carbide‐like junction at the ethylene oxide/Al interface during the thermal evaporation is of essential importance to the extraction of electrons through the Al electrode. The performance of P3HT:PCBM‐based solar cells can be optimized by modulating the co‐evaporation ratios of the PEGDE polymer with Al metal due to the changes in the work functions of the electrodes. The VOC and η for devices fabricated with Al electrode are 0.44 V and 1.64%, respectively, and significantly improve to 0.58 V and 4.00% when applying the PEGDE:Al(2:1)/Al electrode. This research leads to a novel electrode design – free of salts, additives, complicated syntheses, and having tunable work function – for fabricating high‐performance photovoltaic cells.
A unique process is developed by thermally co‐evaporating a poly(ethylene oxide)‐based polymer with Al metal simultaneously at different ratios in vacuum (10−6 Torr) to prepare the electrode buffers for polymer bulk‐heterojunction solar cells. This research leads to a novel electrode design – free of salts, additives, and complicated synthesis, and having tunable work function – for fabricating high‐performance photovoltaics.
We demonstrated the good performance of inorganic inverted CH3NH3PbI3 perovskite-based solar cells (SCs) with glass/ITO/NiOx/CH3NH3PbI3 perovskite/C60/ room temperature (RT)-sputtered ZnO/Al ...structure. We adopted spin coating and RT sputtering for the deposition of NiOx and ZnO, respectively. The inorganic hole and electron transport layer of NiOx and RT-sputtered ZnO, respectively, could improve the open-circuit voltage (VOC), short-circuit current density (JSC), and power conversion efficiency (η%) of the SCs. We obtained inorganic inverted CH3NH3PbI3 perovskite-based SCs with a JSC of 21.96 A/cm2, a VOC of 1.02 V, a fill factor (FF%) of 68.2%, and an η% of 15.3% despite the sputtering damage of the RT-sputtered ZnO deposition. Moreover, the RT-sputtered ZnO could function as a diffusion barrier for Al, moisture, and O2. The inorganic inverted CH3NH3PbI3 perovskite-based SCs demonstrated improved storage reliability.
We have demonstrated the fabrication and characterization of single-layered hybrid polymer-quantum-dot light-emitting diodes (PQD-LEDs) with the emissive composite film of ...2,3-dibutoxy-1,4-poly(phenylene vinylene) (DBPPV) and inorganic CdSe-ZnS core/shell quantum dots (QDs). It is observed that both the electrical and optical characteristics are significantly improved by adjusting the thickness of the emissive layer. For the device with composite film thickness of 103 nm, the turn-on voltage is 4.1 V, and the maximum luminance of 4100 cd/m as well as maximum luminous efficiency of 1.35 cd/A are achieved at 9.6 and 7.6 V, respectively. The optimum emission contribution of luminescence from QDs to the whole luminance is 38%. However, the QD luminescence is mainly limited by the Foumlrster energy transfer mechanism and no obvious QD-related injected carrier trapping is observed. To our knowledge, this is the first demonstration of PQD-LEDs that consist of DBPPV and CdSe-ZnS QDs.
This work investigates the correlations between the morphological characteristics of the active layers, comprised of poly(3-hexylthiophene) and 6,6-phenyl-C
61-butyric acid methyl ester, and the ...photovoltaic performance of polymer-based solar cells. The active layers were deposited by spin-coating the polymer solutions under various conditions and, then, characterized by atomic force microscopy, X-ray diffraction, UV/Vis and Raman spectroscopy. Results of this study indicate that solar cells employing the slow-solvent-vapor-treatment blend films as the active layers exhibit the enhanced power conversion efficiency (3.0%), short-circuit (8.71 mA/cm
2) current and fill factor (0.59) than that of as-cast and fast-thermal-annealing blend films.
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