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An efficient visible-light-responsive surface charge transfer complex AA-TiO2 based dye-sensitized solar cell
摘要： This work investigated a new strategy for visible light responsive dye-sensitized solar cell: the ligand-to-metal charge transfer (LMCT) takes place between TiO2 nanoparticles and ascorbic acid (AA). The surface LMCT complex AA-TiO2 extended the spectral responsive range to 800 nm and exhibited prominent visible light activity, enhancing utilization of the solar spectrum. The optimal photovoltaic conversion efficiency of the visible-light-responsive AA-TiO2 based dye-sensitized solar cell reach value of 3.50%. The low-cost, non-toxic and environment friendly surface adsorbate AA will demonstrate a feasible approach for replacing the most common used ruthenium complex dyes, thereby offering a strategy for development of low-cost and high efficiency DSSCs.
关键词： Dye-sensitized solar cell,Surface complex,Ligand-to-metal charge transfer (LMCT),Ascorbic acid,Visible light activity
更新于2025-09-23 15:19:57
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Spectroscopic Studies of Charge-Transfer Character and Photoresponses of F <sub/>4</sub> TCNQ-Based Donora??Acceptor Complexes
摘要： F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) is used widely as a hole-doping agent in photoresponsive organic semiconducting materials, yet relatively little is known about the photoresponses of the F4TCNQ?? anion generated via doping. Furthermore, there is still relatively little systematic exploration of how the properties of the local material or chemical environment impacts the driving force for generating these charge-transfer complexes. Here we present spectroscopic and photophysical studies of F4TCNQ in charge-transfer complexes (CTCs) with the electron donor N,N′-diphenyl-N-N′-di-p-tolylbenzene-1,4-diamine (MPDA) both in dichloroethane solution and polystyrene matrices. Integer charge transfer (ICT) between donor and acceptor occurs readily in dichloroethane solvent to form F4TCNQ??:MPDA+ CTCs, due to a ～150 mV difference in MPDA+/MPDA and F4TCNQ/F4TCNQ?? reduction potentials. Ultrafast spectroscopic studies of the CTC as well as electrochemically generated F4TCNQ?? and MDPA+ reveal that the photoresponses of these CTCs are dominated by that of the dopant anion, including rapid deactivation (800 fs) after excitation to the anion D1 excited state, followed by slower (～10 ps) vibrational cooling in the anion D0 state. Excitation to the higher-lying D2 state results in a rapid relaxation to the D1 state, in contrast to direct D2 → D0 relaxation previously observed for F4TCNQ?? in the gas phase. CTCs embedded in polystyrene (PS) matrices are observed to lose their integer charge-transfer character upon evaporation of solvent, as evidenced by changes to electronic and vibrational absorption features associated with F4TCNQ??. This change is attributed to the loss of solvent stabilization of the ion pair formed through the charge-transfer reaction. Ultrafast spectral measurements reveal that the photoresponses of the partial charge-transfer (PCT) species embedded in PS are still highly similar to those of the ICT species and unlike that of neutral F4TCNQ, implying the electronic properties of the PCT state are likewise dominated by properties of the reduced acceptor molecule. We conclude that excitation of ICT or PCT states introduces optical losses for photoresponses of doped organic semiconductor materials due to the large anion absorption cross section and its rapid, dissipative deactivation dynamics.
关键词： photoresponses,ultrafast spectroscopy,charge-transfer complexes,F4TCNQ,organic semiconducting materials
更新于2025-09-23 15:19:57
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Interaction of ZnO nanorods with plasmonic metal nanoparticles and semiconductor quantum dots
摘要： We model the enhancement of near band edge emission from ZnO nanorods using plasmonic metal nanoparticles and compare it with emission enhancement from ZnO with semiconducting quantum dots. Selected CdSe quantum dots with absorption energies close to those of Ag and Au nanoparticles are chosen to construct model systems with ZnO to comprehend the role of ZnO’s intrinsic defects and plasmonic excitation in realizing the spectrally selective luminescence enhancement. Excitation wavelength dependent photoluminescence spectra along with theoretical models quantifying the related transitions and plasmonic absorption reveal that a complex mechanism of charge transfer between the ZnO nanorods and metal nanoparticles or quantum dots is essential along with an optimal energy band alignment for realizing emission enhancement. The theoretical model presented also provides a direct method of quantifying the relative transition rate constants associated with various electronic transitions in ZnO and their change upon the incorporation of plasmonic nanoparticles. The results indicate that, while the presence of deep level defect states may facilitate the essential charge transfer process between ZnO and the plasmonic nanoparticles, their presence alone does not guarantee UV emission enhancement and strong plasmonic coupling between the two systems. The results offer clues to designing novel multicomponent systems with coupled plasmonic and charge transfer effects for applications in charge localization, energy harvesting, and luminescence enhancement, especially in electrically triggered nanophotonic applications.
关键词： ZnO nanorods,plasmonic metal nanoparticles,semiconductor quantum dots,luminescence enhancement,charge transfer
更新于2025-09-23 15:19:57
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Direct dynamic evidence of charge separation in a dyea??sensitized solar cell under operando conditions by Raman spectroscopy
摘要： Interfaces play an important role in enhancing the energy conversion performance of dye-sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but almost all studies only performed on a portion of DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamic observations of the photovoltaic conversion process from a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also successfully identified molecular-scale dynamic evidence that the bands from the C═C of 2,2’-bipyridyl (bpy), the S═C═N of NCS ligand and photochemical products show reasonably strong intensity and frequency changes, which clearly demonstrates that they are important pathways of charge separation. Furthermore, RR spectroscopy also be applicable to quickly evaluate the performance of DSCs.
关键词： dye-sensitized solar cell,semiconductor,TiO2 nanotube array,Raman spectroscopy,charge transfer
更新于2025-09-23 15:19:57
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Synchronous surface and bulk composition management for red-shifted light absorption and suppressed interfacial recombination in perovskite solar cells
摘要： Organic small molecules ammonium halide salts (AHSs) are widely used to suppress the non-radiative charge recombination of solution-processed halide perovskite films with defective surface and unfavorable energy level for enhanced photovoltage, but more often than not at a cost of enlarging the bandgap of perovskite materials, which limits the light absorption and thus photocurrent density. In addition, there is still a lack of fundamental understanding and visual characterization of the surface and bulk composition change upon subsequent surface treatment with heterogeneous ingredients. Herein, we report and identify that AHS soaking treatment enables the formation of δ-FAPbI3 on the surface of the perovskite film for defect passivation function, thus reducing the interfacial recombination loss and increasing photovoltage. Meanwhile, the AHS molecules diffuse and alloy with the bulk perovskite material to reduce the bandgap, red-shifting the absorption region and thus increasing the photocurrent. Blade-coated perovskite solar cells (PSCs) prepared via AHS treatment achieved a champion power conversion efficiency (PCE) of 21.9% with a high open-circuit voltage (Voc) up to 1.18 V under AM 1.5G sun illumination, which is remarkably higher than the pristine PSCs without any treatment (19.2%), and outperforms other blade-coated PSCs, regardless of their perovskite compositions. Surface treatment of perovskite films with functional, organic small molecules is a promising strategy for rational composition management and favorable gradient distribution, which are beneficial for realizing efficient and stable PSCs.
关键词： light absorption,perovskite,charge transfer,defect passivation,solar cells
更新于2025-09-23 15:19:57
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Quantum Dots and Applications
摘要： It is the unique size-dependent band gap of quantum dots (QDs) that makes them so special in various applications. They have attracted great interest, especially in optoelectronic ?elds such as light emitting diodes and photovoltaic cells, because their photoluminescent characteristics can be signi?cantly improved via optimization of the processes by which they are synthesized. Control of their core/shell heterostructures is especially important and advantageous. However, a few challenges remain to be overcome before QD-based devices can completely replace current optoelectronic technology. This Special Issue provides detailed guides for synthesis of high-quality QDs and their applications. In terms of fabricating devices, tailoring optical properties of QDs and engineering defects in QD-related interfaces for higher performance remain important issues to be addressed.
关键词： quantum dots,luminescent solar concentrator,photoluminescent,photovoltaic,photodetector,charge transfer,electroluminescent
更新于2025-09-23 15:19:57
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Delayed Fluorescence Emitter Enables Near 17% Efficiency Ternary Organic Solar Cells with Enhanced Storage Stability and Reduced Recombination Energy Loss
摘要： Charge transfer state (CT) plays an important role in exciton diffusion, dissociation, and charge recombination mechanisms. Enhancing the utilization and suppressing the recombination process of CT excitons is a promising way to improve the performance of organic solar cells (OSCs). Here, an effective method is presented via introducing a delayed fluorescence (DF) emitter 3,4-bis(4-(diphenylamino)phenyl) acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile (APDC-TPDA) in OSCs. The long-lifetime singlet excitons on APDC-TPDA can transfer to polymer donors to prolong exciton lifetime, which ensures sufficient time for diffusion and dissociation. Concurrently, the high triplet energy level (T1) of the DF material can also prevent the reverse energy transfer from CT to T1. APDC-TPDA-containing ternary OSCs shows a high PCE of 16.96% with a reduced recombination energy loss of 0.46 eV. It is noteworthy that the ternary OSC also exhibits superior storage stability. After 55 days of storage, the PCE of the ternary OSC still retains about 96% of its primitive state. Furthermore, this ternary strategy is efficient and universally applicable to OSCs, and positive results can be obtained in different systems with different DF emitters. These results indicate that the ternary strategy provides a new design idea to realize high performance OSCs.
关键词： delayed fluorescence,recombination energy loss,organic solar cells,charge transfer state,storage stabile solar cells
更新于2025-09-23 15:19:57
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Cyclic versus straight chain oligofuran as sensor: A detailed DFT study
摘要： This study is a novel approach for exploring the sensitivity and selectivity of cyclic oligofuran (5/6/7CF) toward gaseous analytes and their comparison with straight chain analogues (5/6/7SF). The work is not only vital to understand the superior sensitivity but also for rational design of new sensors based on cyclic ring structures of oligofuran. Interaction of cyclic and straight chain oligofuran with NH3, CO, CO2, N2H4, HCN, H2O2, H2S, CH4, CH3OH, SO2, SO3 and H2O analytes is studied via DFT calculation at B3LYP-D3/6-31++G (d, p) level of theory. The sensitivity and selectivity are illustrated by the energetic parameters (Ebind, SAPT0 energies, NCI analysis) electronic properties (H-L gap, percentage of average energy gap, CHELPG charge transfer, DOS spectra) and UV-Vis analysis. All these properties are simulated at B3LYP/6-31G (d) level of theory while UV-Vis is calculated at TD-DFT method. Cyclic oligofuran has high binding energy with analytes compared to 5/6/7SF which corresponds the higher sensitivity of 5/6/7CF. Furthermore, the cyclization of oligofuran significantly improve the sensitivity and selectivity of the system. Alteration in electronic properties of 5/6/7CF and 5/6/7SF is remarkably high upon complexation with SO2 and SO3. Further the stability of rings (5, 6 and 7 membered cyclic oligofurans) and their SO3 complexes is also confirmed by molecular dynamics calculations. The finding of the work clearly suggests that the cyclic geometry enhances not only sensitivity but also selectivity of conducting polymers (oligofuran).
关键词： Oligofuran,Noncovalent interaction index (NCI),Density Functional Theory (DFT),CHELPG charge transfer,Symmetry adopted perturbation theory (SAPT)
更新于2025-09-23 15:19:57
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Versatile Phosphole Derivatives with Photovoltaic, Light-Emitting, and Resistive Memory Properties
摘要： A series of dithienophosphole compounds has been successfully synthesized and characterized by photophysical, electrochemical, and thermal studies. Possessing the electron-deficient dithienophosphole oxide moiety, these compounds are found to display strong intramolecular charge transfer character and exhibit high photoluminescence quantum yields of up to 0.68. Taking advantage of these phosphole-based the properties, compounds have been applied as active materials in the fabrication of organic photovoltaics (OPVs), organic light-emitting devices (OLEDs) and organic resistive memory devices. Satisfactory performances with power conversion efficiencies of up to 4.23% for OPV devices, external quantum efficiencies of up to 3.0% for OLEDs, and binary resistive memories with retention time of over 10000 s and distinctive OFF/ON current ratio of 1:107 have been realized based on these dithienophosphole compounds. These findings revealed the multifunctional behavior of these dithienophosphole compounds and represent for the first time the use of phosphole-based small molecules as donor materials for the vacuum-deposited OPV devices.
关键词： OPVs,dithienophosphole derivatives,multifunctional materials,resistive memory devices,fluorescent OLEDs,intramolecular charge transfer
更新于2025-09-23 15:19:57
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A novel hot exciton blue fluorophores and white organic light-emitting diodes with simplified configuration
摘要： The two efficient non-doped blue emitters with hybridized local and charge transfer state namely, NDBNPIN and DBTPIN have been synthesised and characterised. These materials are employed as a host for green and red phosphorescent OLEDs. The white device based on DBTPIN:Ir(MDQ)2(acac) (4%) exhibit maximum external quantum efficiency (ηex) ?24.8%; current efficiency (ηc) ?57.1 cdA?1; power efficiency (ηp) ?64.8 lmW?1 with Commission Internationale de l’Eclairage (CIE:0.49, 0.40) than NDBNPIN:Ir(MDQ)2acac (4%) device [ηex ? 23.1%; ηc ?54.6 cd A?1; ηp? 60.0 lm W?1 with CIE (0.47, 0.42)]. Development of blue emitter is crucial in organic light emitting devices (OLEDs) to reduce power consumption effectively1. For an OLED with stable emission the current efficiency (CE) is proportional to external quantum efficiency (?ex): power efficiency (PE) is determined by CE and operating voltage (V) [PE = π CE/V]2–4. Iridium and platinum based phosphorescent complexes and TADF (thermally activated delayed fluorescent materials) exhibit high ?ex, however, suffered with short lifetime and roll-off efficiency and also the production cost of phosphorescent materials are unfavourable for practical applications5. Therefore, low driving voltage with high brightness become the major issue to achieve efficient OLEDs6. In OLEDs, balanced hole: electron recombination leads to formation of CT exciton (charge-transfer) which undergo decay directly or relaxes to LE (local exciton), thus, utilization of both CT exciton and LE provides efficient EL (electroluminescence). From 4-(dicyanomethylene)-2-methyl-6-[4-(dimethylaminostyryl)-4H-pyran] with CT state maximum efficiency have been harvested7–9. Donor–acceptor (D–A) compounds with low % CT leads to RISC (reverse intersystem crossing) process which results high singlet utilisation efficiency(?s), however, colour-purity is still poor due to broadened PL (photoluminescence) and EL (electroluminescence) spectra10–13. D-A architecture with high % LE state leads to higher efficiency because of maximum orbital overlap whereas high % CT provides low efficiency due to partial hole and electron overlap. However, because of small energy splitting (ΔES-T ≈ 0) CT state undergo RISC process 11,12. These issues are overcome, by employing D–A configured emissive materials with results in enhanced ηs HLCT emissive state: stabilised LE and CT states results in ηPL(photoluminance efficiency) and high ηs.. Thus, construction of D–A emitters with HLCT emissive state is novel strategy to design efficient blue emitters.
关键词： hybridized local and charge transfer state,blue emitters,OLEDs,electroluminescence,phosphorescent
更新于2025-09-23 15:19:57