Non-radiative Research Articles

A compact and narrow-band bandpass filter based on substrate integrated waveguide and spoof surface plasmon polaritons for millimeter-wave applications

This paper presents bandpass filter (BPF) comprising substrate integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs), achieving miniaturized size, low insertion loss in the millimeter-wave band. SIW with single-slotted SSPP structure is employing to obtain the transmission zero (TZ) at the low-frequency part, and by introducing the SIW with rhombic periodic walls to enhance the low-frequency rejection. The target passband and TZ of the high-frequency part are realized by increasing the number of etching slots. Furthermore, we innovatively incorporate nonradiative (NR) slots etched below the SSPP structure to gain high out-of-band rejection level. SIW with rhombic periodic walls and slotted SSPP structure as one unit cell is analyzed and demonstrated. Ultimately, the two SIW unit cells are cascaded together to get better out-of-band rejection characteristics and serve as our final design. To validate the proposed design, the BPF prototype is fabricated and measured, showing good electrical performance in terms of high selectivity, low loss, and compact size.

Amine‐Free Multi‐Faceted CsPbBr3 Nanocrystals for Complete Suppression of Long‐Lived Dark States

AbstractConventional amine‐capped perovskite nanocrystals (A‐PNCs) often show microscopic fluctuation (blinking) of photoluminescence (PL) between bright and near‐background (dark) states. The transient dark phases spanning milliseconds (ms) to several seconds timescale typically owe to the non‐radiative (NR) fate of charge carriers in crystal defect states, limiting the PNC's efficiency in optoelectronics. A PL study of a novel trioctylphosphine (TOP) capped rhombic cuboctahedron‐shaped amine‐free (AF) PNC is presented, demonstrating their fascinating nonblinking nature. While oleylamine‐capped hexahedron A‐PNCs as a reference system show long dark states, their population is completely suppressed in ≈90% of AF‐PNCs with random large‐amplitude PL fluctuations several times above the background. The PL trajectories of AF‐PNCs primarily comprise constant power spectral densities (PSDs) which are unprecedented and deviate from power‐law distribution as observed for A‐PNCs and most of the other blinking nanocrystals. Such signature of PSDs and frame‐by‐frame intensity jump analysis indicate a fast (<<ms) timescale charge‐carrier dynamics governing the PL emission of AF‐PNCs, likely involving short‐lived metastable states. Besides, long‐term stability and suppressed dark phases in ≈70% AF‐PNCs even 90 days after the synthesis is noteworthy. Altogether the study provides exceptional optical characteristics of photostable amine‐free PNCs which would be attractive to exploit in commercial display applications.

Tuning Acceptor Composition in Ternary Organic Photovoltaics–Impact of Domain Purity on Non‐Radiative Voltage Losses

AbstractExaggerated charge losses from excited to charge transfer (CT) and ground states in bulk heterojunction (BHJ) structures results in small voltages (< 1 V) for organic solar cells (OSCs). Characterizing morphology‐voltage loss correlations is difficult due to the complexity of BHJ structures but promises the realization of 20% efficiency for OSCs. By utilizing two similar non‐fullerene acceptors (NFA) in a ternary blend, a pseudo‐binary system is constructed to control the acceptor composition and donor‐acceptor (D‐A) miscibility. Within the framework of miscibility‐morphology controlled device photovoltaics, it is found that higher D‐A miscibility results in enhanced domain purity, which is associated with inefficient excitons dissociation and improves the excited and CT state emission, thereby resulting in enhanced electroluminescence efficiency to reduce the non‐radiative (NR) loss contribution to device voltage. The simple but effective composition mediated morphology control identifies domain purity as one key feature to lower the NR recombination in high quantum yield polymer/NFA blends.

Structural and optical conduct of cool white-light emanating BaGd2ZnO5:Dy3+ nanocrystals for white LEDs

An orthorhombic symmetry type BaGd2ZnO5:Dy3+ nanocrystals with luminance of cool white-color light have been fabricated via urea assisted combustion methodology. Morphological analysis revealed the agglomerated particles with non-uniform shape having crystal-size of 30–40 nm. Optimized amount of dopant (Dy3+) was examined to be x = 3 mol%, after the occurrence of quenching phenomenon. The logical pathways for quenching mechanism has been determined as non-radiative (NR) relaxations of energy via exchange-type interrelations as validated by Inokuti-Hirayama (I-H) and Dexter’s theory. Fabricated nano-powders represents two band located at 492 nm (bluish) and at 581 nm (yellowish). Band gap, decay life time and quantum efficiency of optimal powder were found as 4.71 eV, 0.7049 ms and 93.9% respectively. White-light emanation is reflected in terms of CIE color-parameters like color-coordinates of white regions (0.2869, 0.3876), color purity of 30 × 10−2 and CCT values as 7206.2 K, which have been in congruence with standard coordinates of commercial LEDs and NTSE and thus, authenticate their optimistic applicability for advanced illuminating devices.

ATR Inhibitor M6620 (VX-970) Enhances the Effect of Radiation in Non-Small Cell Lung Cancer Brain Metastasis Patient-Derived Xenografts.

M6620, a selective ATP-competitive inhibitor of the ATM and RAD3-related (ATR) kinase, is currently under investigation with radiation in patients with non-small cell lung cancer (NSCLC) brain metastases. We evaluated the DNA damage response (DDR) pathway profile of NSCLC and assessed the radiosensitizing effects of M6620 in a preclinical NSCLC brain metastasis model. Mutation analysis and transcriptome profiling of DDR genes and pathways was performed on NSCLC patient samples. NSCLC cell lines were assessed with proliferation, clonogenic survival, apoptosis, cell cycle, and DNA damage signaling and repair assays. NSCLC brain metastasis patient-derived xenograft models were used to assess intracranial response and overall survival. In vivo IHC was performed to confirm in vitro results. A significant portion of NSCLC patient tumors demonstrated enrichment of DDR pathways. DDR pathways correlated with lung squamous cell histology; and mutations in ATR, ATM, BRCA1, BRCA2, CHEK1, and CHEK2 correlated with enrichment of DDR pathways in lung adenocarcinomas. M6620 reduced colony formation after radiotherapy and resulted in inhibition of DNA DSB repair, abrogation of the radiation-induced G2 cell checkpoint, and formation of dysfunctional micronuclei, leading to enhanced radiation-induced mitotic death. The combination of M6620 and radiation resulted in improved overall survival in mice compared with radiation alone. In vivo IHC revealed inhibition of pChk1 in the radiation plus M6620 group. M6620 enhances the effect of radiation in our preclinical NSCLC brain metastasis models, supporting the ongoing clinical trial (NCT02589522) evaluating M6620 in combination with whole brain irradiation in patients with NSCLC brain metastases.

Heterogeneities and Emissive Defects in MAPbI3 Perovskite Revealed by Spectrally Resolved Luminescence Blinking

AbstractThe fate of excited charge carriers in metal halide perovskite semiconductors is influenced by energetic disorder and defects. Here, photoluminescence (PL) blinking is used to probe metastable nonradiative (NR) centers and the nanoscale energy landscape. Temporal activation of an NR center creates a local region with increased NR recombination. Activation and deactivation of this local PL quenching does not only lead to PL blinking, but also to fluctuations of the PL spectra, if the crystal is inhomogeneous in the sense that the PL emission spectrum is slightly different from one location to another. It resembles the spectral hole‐burning technique; however, here the eliminated excited states are chosen by their spatial localization close to the quencher. In MAPbI3, PL spectral fluctuations at low temperature reveal energetic inhomogeneities on the order of 5 to 10 meV. Quenching of the main PL band is often found to correlate with an increase of the low‐energetic tail of the PL spectra, which is attributed to partially radiative recombination of charges captured by the NR center. The transition energy of the NR center is found to be only ≈80 meV smaller than the bandgap, implying that the underlying defect cannot be a single mid‐bandgap state.

FGFR Inhibition Enhances Sensitivity to Radiation in Non-Small Cell Lung Cancer.

FGFRs are commonly altered in non-small cell lung cancer (NSCLC). FGFRs activate multiple pathways including RAS/RAF/MAPK, PI3K/AKT, and STAT, which may play a role in the cellular response to radiation. We investigated the effects of combining the selective FGFR 1-3 tyrosine kinase inhibitor AZD4547 with radiation in cell line and xenograft models of NSCLC. NSCLC cell lines were assessed with proliferation, clonogenic survival, apoptosis, autophagy, cell cycle, and DNA damage signaling and repair assays. In vivo xenografts and IHC were used to confirm in vitro results. NSCLC cell lines demonstrated varying degrees of FGFR protein and mRNA expression. In vitro clonogenic survival assays showed radiosensitization with AZD4547 in two NSCLC cell lines. In these two cell lines, an increase in apoptosis and autophagy was observed with combined radiation and AZD4547. The addition of AZD4547 to radiation did not significantly affect γH2AX foci formation. Enhanced xenograft tumor growth delay was observed with the combination of radiation and AZD4547 compared with radiation or drug alone. IHC results revealed inhibition of pMAPK and pS6 and demonstrated an increase in apoptosis in the radiation plus AZD4547 group. This study demonstrates that FGFR inhibition by AZD4547 enhances the response of radiation in FGFR-expressing NSCLC in vitro and in vivo model systems. These results support further investigation of combining FGFR inhibition with radiation as a clinical therapeutic strategy.

Elucidating the excited-state dynamics behavior in near-infrared Bodipy dye and aggregates toward biophotonics

Photo-induced excited-state dynamics within organic materials fundamentally determine their photophysical properties for various applications, and thus understanding the primary excited-state dynamics behavior is of fundamental and practical significance. Until recently, the excited-state dynamics of organic materials towards biophotonics have been rarely studied, although numerous endeavors have been devoted to the design of organic materials for biophotonics. Herein, various spectroscopy technologies including femtosecond transient absorption (fs-TA) spectroscopy clearly reveal a totally different excited state dynamics behavior within Bodipy monomer (2B-BDP dye) and aggregates (2B-BDP NPs), indicating strongly morphology dependent character. 2B-BDP dye undergoes an ultrafast conversion from S1 to intramolecular charge transfer (ICT) state for subsequent photoluminescence (PL) and nonradiative (NR) decay, while 2B-BDP NPs show an accelerated excited-state deactivation mainly through S1→S0 NR decay. The potential bioapplications based on the corresponding excited state dynamics behavior are discussed together with experimental results. Interestingly, the accelerated NR decay in 2B-BDP NPs does not yield a stronger photoacoustic (PA) signal than that in 2B-BDP dye, which violates the conventional wisdom that faster NR decay would benefit the photothermal effects for better photoacoustic imaging (PAI). These insightful and fundamental observations of the excited-state dynamics may contribute an alternative approach at the molecular level towards the future design of functional Bodipy-based organic molecules with desirable performances.

Interfacial and Bulk Nanostructures Control Loss of Charges in Organic Solar Cells.

Organic solar cells (OSCs) have emerged as one promising sustainable energy resource since the introduction of state-of-the-art bulk heterojunction (BHJ) device structure in early 1990s. Impressively developed molecular design methodologies in the past decade have led researchers toward utilizing more suitable pairs of low (p-type) and high (n-type) electron affinity organic semiconducting materials. Among other attributes, versatile absorption capabilities of these materials highlight their favorable utilization in a single layer BHJ structure. Interaction of these verstile organic materials may lead to explicit interfaces, phase distributions, and crystalline nanostructures. Structural characterization techniques involving soft and hard X-rays have enabled us to measure these morphology parameters quantitatively including their string correlation with photovoltaic (PV) parameters. Favorable processing techniques have been adopted to realize auspicious interfacial areas and charge percolations in bulk toward efficient short circuit current (JSC) and fill factor (FF) values. Collaborative efforts in the fields of chemical structure design of materials, device characterization, and engineering have pushed the power conversion efficiencies (PCEs) of OSCs to 16%. However, the single layer BHJ structure still requires further optimizations for the extension of their PCEs toward the theoretical limit. Maximum utilization of solar energy by organic blend films is the key to match their potential with inorganic/perovskite solar cells. Having comparable JSC and FF values in organic versus inorganic photovoltaic devices, open circuit voltage (VOC) is the only PV parameter limiting the development of OSCs in comparison to their inorganic competitors. This is due to unfavorable competition between rates of charge generation and recombination. Loss of charges during these generation and recombination processes account for the energy loss of the device, ranging from 0.6 to 1.0 V in state-of-the-art OSCs. Highly efficient (14-16%) single layer BHJ devices usually suffer from high energy loss with VOC limited to 0.9 V. Comparatively, devices with reported VOC > 0.9 V suffer from poor JSC and FF values due to unfavorable interfacial ordering and bulk crystalline nanostructures. First part of the Account will address the charge losses during their transfer (interfacial losses) and influential role of interfacial nanostructures in controlling them toward efficient JSC and VOC values. Later, we will discuss losses during exciton diffusion and free charge transport (bulk losses) toward limited charge extraction. We will debate about the role of donor/acceptor nanostructures in correlation with influential photophysics studies to control these losses in small molecule (SM) acceptor based devices. We search for exaggerated crystalline phases of SM acceptor in competition with polymer donor to realize balanced and more efficient charge percolations. These improved diffusion and transport bulk nanostructures will suppress nonradiative (NR) pathways and bulk charge losses toward simultaneous enhancement of FF and VOC values. Favorable interfacial and bulk morphology will drive efficient diffusion, transfer, transport, and extraction of charges in organic blend films. This Account will guide chemists and engineers to optimize chemical structure design and blend film nanostructures toward suppressed energy loss of OSCs.

Manipulating Nonradiative Decay Channel by Intermolecular Charge Transfer for Exceptionally Improved Photothermal Conversion.

In-depth studies of nonradiative (NR) decay, seeking to maximize NR decay rate or manipulate other NR decay channels, are of greatest significance for improving the photothermal conversion efficiency (η) of organic materials for phototheranostics; however, to date, relevant work remains scarce. Here, we present an insightful study of NR decay in BODIPY (BDP) dye, in an aggregated state, i.e., in BDP nanoparticles (BDP NPs), which show an efficient additional NR decay channel from the aggregation-stabilized intermolecular charge transfer (CT) state, resulting in exceptionally high η (61%) for highly efficient phototheranostics in vivo. BDP NPs exhibit two ultrafast NR decay channels with ultrashort lifetimes of 1.7 and 50 ps, which is in stark contrast to the only S1 → S0 NR channel with a long lifetime of 373 ps in the isolated BDP dye. More importantly, the ultrafast NR channel (1.7 ps) in BDP NPs depletes a substantial portion of the excited-state population (71%), which accounts for its much better photothermal effect as compared with the isolated BDP dye. Finally, BDP NPs display a highly efficient photoacoustic imaging (PAI) guided photothermal therapy (PTT) of tumors in live mice. This study presents a deeper fundamental understanding of NR decay in organic materials, setting a valuable guideline that may be widely applicable to similar molecular structure to develop more advanced organic materials not only for photothermal-related applications.

Enhanced luminescence properties of InAs nanowires via organic and inorganic sulfide passivation

InAs nanowires (NWs) have been considered to be highly suitable for future nanoscale photonic applications in mid-wave infrared region. However, progress in this area has been seriously hampered because of the poor radiative efficiency of InAs NWs attributed to their non-radiative (NR) surface. Herein, we demonstrated that a significant improvement of optical performances of InAs NWs grown by chemical vapor deposition could be achieved via sulfur passivation process. Luminescence properties of InAs NWs via organic sulfide (ODT) and inorganic sulfide ((NH4)2S) passivation were investigated by detailed photoluminescence (PL) measurement, which exhibited ∼17-fold enhancement in the intensity of optical emission compared to unpassivated InAs NWs. Moreover, the results of this investigation revealed that compared to ODT passivation, (NH4)2S passivation provided a more effective method to enhance the luminescence intensity even up to room temperature. This improvement of optical emission arises from the efficient passivation of surface defect states which act as competing NR centers. Furthermore, the stability of the passivated InAs NWs was investigated by PL measurement as a function of storage time in air. These findings are important for the successful implementation of optoelectronic devices based on InAs NWs.

Increasing N content in GaNAsP nanowires suppresses the impact of polytypism on luminescence

Cathodoluminescence (CL) and micro-photoluminescence spectroscopies are employed to investigate effects of structural defects on carrier recombination in GaNAsP nanowires (NWs) grown by molecular beam epitaxy on Si substrates. In the NWs with a low N content of 0.08%, these defects are found to promote non-radiative (NR) recombination, which causes spatial variation of the CL peak position and its intensity. Unexpectedly, these detrimental effects can be suppressed even by a small increase in the nitrogen composition from 0.08% to 0.12%. This is attributed to more efficient trapping of excited carriers/excitons to the localized states promoted by N-induced localization and also the presence of other NR channels. At room temperature, the structural defects no longer dominate in carrier recombination even in the NWs with the lower nitrogen content, likely due to increasing importance of other recombination channels. Our work underlines the need in eliminating important thermally activated NR defects, other than the structural defects, for future optoelectronic applications of these NWs.

Origin of Photocurrent and Voltage Losses in Organic Solar Cells

AbstractOrganic solar cells (OSCs) have recently achieved power conversion efficiencies (PCEs) of over 16%. However, there still exist large losses in photocurrent and/or voltage in state‐of‐the‐art OSCs, making the PCEs still far below those of inorganic counterparts. Here, the factors and electronic processes for photocurrent and voltage losses are identified and discussed in the framework of device physics and photophysics. To simultaneously obtain both high photocurrent density and low voltage loss toward 20% PCEs, it is crucial to suppress the non‐radiative (NR) recombination of the lowest charge‐transfer (CT) state at the donor–acceptor interface. In principle, theoretical simulations can provide molecular insight into the origin of these losses, which is essential to guide material design. In particular, the authors highlight the importance of the local interface morphologies and the vibronic couplings on suppressing the NR decay of the lowest CT state according to recent theoretical studies.

Development of Red Exciplex for Efficient OLEDs by Employing a Phosphor as a Component.

Exciplexes are ideal candidates as effective thermally activated delayed fluorescence (TADF) emitters. However, efficient orange and red TADF exciplexes have been reported seldomly, because their significant non-radiative (NR) decay of excited states lead to unavoidable energy loss. Herein, we propose a novel strategy to construct efficient red TADF exciplexes by introducing phosphor as one component. Due to the strong spin–orbit coupling of heavy metal (e.g., Ir, Pt, et al.) ion cores, the NR decays will be evidently decreased for both singlet and triplet excitons, reducing the undesired exciton waste. Moreover, compared with the conventional exciplexes, phosphorescence plays an important role for such novel exciplexes, further improving the exciton utilization. Based on this strategy, we fabricated a red exciplex containing 1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl)tris(diphenylphosphine oxide) (PO-T2T) and tris(2-phenylpyridine) iridium(III) (Ir(ppy)3) as components and realize a red emission with a peak at 604 nm, a CIE coordinate of (0.55, 0.44), and a high maximum external quantum efficiency of 5% in organic light-emitting device. This efficiency is 2.6 times higher than that of the device based on the conventional red exciplex emitter, proving the superiority of our novel strategy to construct TADF exciplexes with phosphors.

PGAM5/FUNDC1/BCL-xL/DRP1 Axis Determines the Mode of Cell Death Induced by Ionizing Radiation in Non–small Cell Lung Cancer

Radiation-induced tumor cell death is widely attributed to multiple distinct mechanisms, mainly including autophagy, apoptosis and necrosis. However, a critical unanswered question is which death pathway a tumor cell chooses in response to various fractionated doses of ionizing radiation (IR). Mitochondrial pathways control both cell apoptosis and necrosis, and play roles in autophagy. The aim of this study was to investigate the role and mechanism of the mitochondrial-dependent cell death regulated by PGAM5/FUNDC1/BCL-xL/DRP1 axis in radiotherapy response of non-small cell lung cancer. Cell death of A549 and Calu-3 NSCLC cell lines induced by various fractionated doses of X-ray radiation (0, 2, 4, 6, 8, 12, 15, 20 Gy/Fraction and 2Gy×9Fraction) was detected by electron microscopy, western blotting, and flow cytometry. Protein interactions were detected by immunofluorescence and immunoprecipitation. Relative low-dose fractionated radiation (LDFRT, <6 Gy /Fraction) were used to induce apoptosis, whereas hypofractionated radiation (HFRT, 6–20 Gy/Fraction) was chosen to induce necrosis in both A549 and Calu-3 cells. Our results demonstrated that LDFRT induced degradation of BCL2-like 1 (BCL2L1), a prominent anti-apoptosis molecule, and released the mitochondrial phosphatase PGAM5 from BCL2L1, which led to its activation and subsequent dephosphorylation of FUN14 domain-containing protein-1 (FUNDC1) at Ser13. The dephosphorylated form of FUNDC1 interacted with light chain 3 (LC3) and induced mitophagy. In addition, peak levels of mitophagy appeared at about 8 hours after 6Gy/Fraction X-ray irradiation in A549, and 4Gy/Fraction X-ray irradiation in Calu-3 cells. Interestingly, the receptor-interacting protein kinase (RIP)1/RIP3 necrosome complex was formed and recruited to the mitochondrial surface at HFRT and then activated PGAM5, dynamin-related protein (Drp1), and mixed lineage kinase domain-like (MLKL) to execute mitochondrial fragmentation and programed cell necrosis. It is worth mentioning that HFRT did not notably induce degradation of BCL2L1 or mitophagy. The PGAM5/FUNDC1/BCL-xL/DRP1 axis might determine mitochondrial fate and the mode of cell death in response to various fractionated doses of X-ray radiation in NSCLC. Targeting these pathways will be useful to understand radiation-induced cell death and may improve the radiotherapeutic effect on human cancers.

FLIP: A Targetable Mediator of Resistance to Radiation in Non-Small Cell Lung Cancer.

Resistance to radiotherapy due to insufficient cancer cell death is a significant cause of treatment failure in non-small cell lung cancer (NSCLC). The endogenous caspase-8 inhibitor FLIP is a critical regulator of cell death that is frequently overexpressed in NSCLC and is an established inhibitor of apoptotic cell death induced via the extrinsic death receptor pathway. Apoptosis induced by ionizing radiation (IR) has been considered to be mediated predominantly via the intrinsic apoptotic pathway; however, we found that IR-induced apoptosis was significantly attenuated in NSCLC cells when caspase-8 was depleted using RNA interference (RNAi), suggesting involvement of the extrinsic apoptosis pathway. Moreover, overexpression of wild-type FLIP, but not a mutant form that cannot bind the critical death receptor adaptor protein FADD, also attenuated IR-induced apoptosis, confirming the importance of the extrinsic apoptotic pathway as a determinant of response to IR in NSCLC. Importantly, when FLIP protein levels were downregulated by RNAi, IR-induced cell death was significantly enhanced. The clinically relevant histone deacetylase (HDAC) inhibitors vorinostat and entinostat were subsequently found to sensitize a subset of NSCLC cell lines to IR in a manner that was dependent on their ability to suppress FLIP expression and promote activation of caspase-8. Entinostat also enhanced the antitumor activity of IR in vivo Therefore, FLIP downregulation induced by HDAC inhibitors is a potential clinical strategy to radiosensitize NSCLC and thereby improve response to radiotherapy. Overall, this study provides the first evidence that pharmacological inhibition of FLIP may improve response of NCSLC to IR. Mol Cancer Ther; 15(10); 2432-41. ©2016 AACR.

NIFTy galaxy cluster simulations – IV. Quantifying the influence of baryons on halo properties

Building on the initial results of the nIFTy simulated galaxy cluster comparison, we compare and contrast the impact of baryonic physics with a single massive galaxy cluster, run with 11 state-of-the-art codes, spanning adaptive mesh, moving mesh, classic and modern SPH approaches. For each code represented we have a dark matter only (DM) and non-radiative (NR) version of the cluster, as well as a full physics (FP) version for a subset of the codes. We compare both radial mass and kinematic profiles, as well as global measures of the cluster (e.g. concentration, spin, shape), in the NR and FP runs with that in the DM runs. Our analysis reveals good consistency (<= 20%) between global properties of the cluster predicted by different codes when integrated quantities are measured within the virial radius R200. However, we see larger differences for quantities within R2500, especially in the FP runs. The radial profiles reveal a diversity, especially in the cluster centre, between the NR runs, which can be understood straightforwardly from the division of codes into classic SPH and non-classic SPH (including the modern SPH, adaptive and moving mesh codes); and between the FP runs, which can also be understood broadly from the division of codes into those that include AGN feedback and those that do not. The variation with respect to the median is much larger in the FP runs with different baryonic physics prescriptions than in the NR runs with different hydrodynamics solvers.

A Facile and Low-Cost Method to Enhance the Internal Quantum Yield and External Light-Extraction Efficiency for Flexible Light-Emitting Carbon-Dot Films.

Solution-processed, non-toxic carbon dots (CDs) have attracted much attention due to their unique photoluminescence (PL) properties. They are promising emissive layers for flexible light-emitting devices. To this end, the CDs in pristine aqueous solutions need to be transferred to form solid-state thin films without sacrificing their original PL characteristics. Unfortunately, solid-state PL quenching induced by extra non-radiative (NR) energy transfer among CDs would significantly hinder their practical applications in optoelectronics. Here, a facile, low-cost and effective method has been utilized to fabricate high-performance CD/polymer light-emitting flexible films with submicron-structured patterns. The patterned polymers can serve as a solid matrix to disperse and passivate CDs, thus achieving high internal quantum yields of 61%. In addition, they can act as an out-coupler to mitigate the waveguide-mode losses, approximately doubling the external light-extraction efficiency. Such CD/polymer composites also exhibit good photo-stability, and thus can be used as eco-friendly, low-cost phosphors for solid-state lighting.

Overcoming metal-induced fluorescence quenching on plasmo-photonic metasurfaces coated by a self-assembled monolayer

We have experimentally shown significant suppression of metal-induced fluorescence (FL) quenching on plasmo-photonic metasurfaces by incorporating a self-assembled monolayer (SAM) of sub-nm thickness. The FL signals of rhodamine dye molecules have been several-ten-fold enhanced by introducing the SAM, in comparison with the previous configuration contacting molecules and metal surfaces.

Modification of Photon Emission Statistics from Single Colloidal CdSe Quantum Dots by Conductive Materials

Colloidal CdSe/ZnS core/shell quantum dots (QDs) can be used to generate single photons at room temperature for promising applications in quantum information sciences. Despite the existence of biexciton (BX) states, they would undergo fast nonradiative Auger relaxation (AR), leading to pure single-exciton (SX) emission, even under high-power excitation. In this work, the fluorescence properties of single colloidal QDs deposited on the conductive ITO surface have been investigated by combining photon correlation spectroscopy and time-tagged, time-correlated single-photon counting (TT-TCSPC) measurement. The conductive materials can introduce extra nonradiative (NR) processes, and thus can significantly alter pristine emission properties, including emission brightness, fluorescence lifetime, and photon emission statistics. We found that such a NR process can strongly quench SX emission but has less effect on BX emission, leading to the increase of the quantum-yield (QY) ratio between BX and SX emission. As ...