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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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Reducing the Singleta??Triplet Energy Gap by Enda??Group ??a???? Stacking Toward Higha??Efficiency Organic Photovoltaics
摘要： To improve the power conversion efficiencies for organic solar cells, it is necessary to enhance light absorption and reduce energy loss simultaneously. Both the lowest singlet (S1) and triplet (T1) excited states need to energetically approach the charge-transfer state to reduce the energy loss in exciton dissociation and by triplet recombination. Meanwhile, the S1 energy needs to be decreased to broaden light absorption. Therefore, it is imperative to reduce the singlet?triplet energy gap (ΔEST), particularly for the narrow-bandgap materials that determine the device T1 energy. Although maximizing intramolecular push?pull effect can drastically decrease ΔEST, it inevitably results in weak oscillator strength and light absorption. Herein, large oscillator strength (≈3) and a moderate ΔEST (0.4?0.5 eV) are found for state-of-the-art A?D?A small-molecule acceptors (ITIC, IT-4F, and Y6) owing to modest push?pull effect. Importantly, end-group π?π stacking commonly in the films can substantially decrease the S1 energy by nearly 0.1 eV, but the T1 energy is hardly changed. The obtained reduction of ΔEST is crucial to effectively suppress triplet recombination and acquire small exciton dissociation driving force. Thus, end-group π?π stacking is an effective way to achieve both small energy loss and efficient light absorption for high-efficiency organic photovoltaics.
关键词： energy loss,triplet recombination,molecular packing,nonfullerene acceptors
更新于2025-09-23 15:19:57
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Monitoring strong coupling in nonlocal plasmonics with electron spectroscopies
摘要： Plasmon-exciton polaritons provide exciting possibilities to control light-matter interactions at the nanoscale by enabling closer investigation of quantum optical effects and facilitating novel technologies based, for instance, on Bose-Einstein condensation and polaritonic lasing. Nevertheless, observing and visualizing polaritons is challenging, and traditional optical microscopy techniques often lead to ambiguities regarding the emergence and strength of the plasmon-exciton coupling. Electron microscopy offers a more robust means to study and verify the nature of plexcitons, but it is still hindered by instrument limitations and resolution. A simple theoretical description of electron beam-excited plexcitons is therefore vital to complement ongoing experimental efforts. Here we apply analytic solutions for the electron-loss and photon-emission probabilities to evaluate plasmon-exciton coupling studied either with the recently adopted technique of electron energy-loss spectroscopy, or with the so-far unexplored in this context cathodoluminescence spectroscopy. Foreseeing the necessity to account for quantum corrections in the plasmonic response, we extend these solutions within the framework of general nonlocal hydrodynamic descriptions. As a specific example, we study core-shell spherical plasmon-molecule hybrids, going beyond the standard local-response approximation through the hydrodynamic Drude model for screening and the generalized nonlocal optical response theory for nonlocal damping. We show that electron microscopies are extremely powerful in describing the interaction of emitters with the otherwise weakly excited by optical means higher-order plasmonic multipoles, a response that survives when quantum-informed models are considered. Our work provides, therefore, both a robust theoretical background and supporting argumentation to the open quest for improving and further utilizing electron microscopies in strong-coupling nanophotonics.
关键词： electron energy-loss spectroscopy,nonlocal hydrodynamic descriptions,cathodoluminescence spectroscopy,quantum plasmonics,Plasmon-exciton polaritons
更新于2025-09-23 15:19:57
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A Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Polymer Solar Cells with a Small Energy Loss
摘要： A Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Polymer Solar Cells with a Small Energy Loss
关键词： energy loss,intramolecular noncovalent interaction,nonfullerene acceptor,organic solar cell
更新于2025-09-23 15:19:57
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Asymmetrically noncovalently fused-ring acceptor for high-efficiency organic solar cells with reduced voltage loss and excellent thermal stability
摘要： Simultaneously broadening the spectral response and reducing the energy loss are challenging tasks in the material design of organic solar cells (OSCs). Herein, a novel asymmetrically noncovalently fused-ring electron acceptor (NFEA) with unilateral alkylthio-substituted thiophene π-bridge, namely IDST-4F, is synthesized. IDST-4F exhibits a broader absorption, higher-lying energy levels, larger dipole moments and suppressed crystallinity than its symmetric counterpart (ID-4F) without the π-bridge. Compared to the devices of PM6:ID-4F, the optimized PM6:IDST-4F-based devices display simultaneously enhanced current density and photovoltage, resulting in an excellent power conversion efficiency (PCE) of 14.3%, which is the highest value among the OSCs based on NFEAs reported in the literature to date. More importantly, the PM6:IDST-4F-based OSCs possess excellent thermal stability with 82% of the initial PCE after thermal treatment at 150 °C for 1200 min. In summary, this study indicates that asymmetrically NFEAs are promising to achieve high efficiency with excellent thermal stability.
关键词： Organic solar cells,Noncovalently fused rings,Thermal stability,Narrow-bandgap acceptor,Energy loss
更新于2025-09-23 15:19:57
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Polymer semiconductors incorporating head-to-head linked 4-alkoxy-5-(3-alkylthiophen-2-yl)thiazole
摘要： Polymer semiconductors incorporating head-to-head linked 4-alkoxy-5-(3-alkylthiophen-2-yl) thiazole? Xin Zhou,?ab Peng Chen,?a Chang Woo Koh,c Sheng Chen,a Jianwei Yu,a Xianhe Zhang,a Yumin Tang,a Luca Bianchi,a Han Guo,*a Han Young Woo and Xugang Guo *a *c Head-to-head linked bithiophenes with planar backbones hold distinctive advantages for constructing organic semiconductors, such as good solubilizing capability, enabling narrow bandgap, and e?ective tuning of frontier molecular orbital (FMO) levels using minimal thiophene numbers. In order to realize planar backbone, alkoxy chains are typically installed on thiophene head positions, owing to the small van der Waals radius of oxygen atom and accompanying noncovalent S/O interaction. However, the strong electron donating alkoxy chains on the electron-rich thiophenes lead to elevated FMO levels, which are detrimental to material stability and device performance. Thus, a new design approach is needed to counterbalance the strong electron donating property of alkoxy chains to bring down the FMOs. In this study, we designed and synthesized a new head-to-head linked building block, 4-alkoxy-5-(3-alkylthiophen-2-yl)thiazole (TRTzOR), using an electron-de?cient thiazole to replace the electron-rich thiophene. Compared to previously reported 3-alkoxy-30-alkyl-2,20-bithiophene (TRTOR), TRTzOR is a weaker electron donor, which considerably lowers FMOs and maintains planar backbone through the noncovalent S/O interaction. The new TRTzOR was copolymerized with benzothiadiazoles with distinct F numbers to yield a series of polymer semiconductors. Compared to TRTOR-based analogous polymers, these TRTzOR-based polymers have broader absorption up to 950 nm with lower-lying FMOs by 0.2–0.3 eV, and blending these polymers with PC71BM leads to polymer solar cells (PSCs) with improved open-circuit voltage (Voc) by ca. 0.1 V and a much smaller energy loss (Eloss) as low as 0.59 eV. These results demonstrate that thiazole substitution is an e?ective approach to tune FMO levels for realizing higher Vocs in PSCs and the small Eloss renders TRTzOR a promising building block for developing high-performance organic semiconductors.
关键词： solar cells,thiazole,head-to-head linked,Polymer semiconductors,energy loss
更新于2025-09-19 17:15:36
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Structure and transport properties of titanium oxide (Ti2O, TiO1+, and Ti3O5) thin films
摘要： Titanium oxides have partially filled or empty d orbital and are stable at various oxidation states with different structures and unique properties. Here, three kinds of titanium oxide thin films of hexagonal Ti2O metal, cubic TiO1+d superconductor, and monoclinic g-Ti3O5 semiconductor, were successfully grown on a-Al2O3 substrates by a pulsed laser deposition technique, through ablating a pure titanium target under different oxygen pressures. The electrical resistivities of these films increase with increasing oxygen content. The metallic behaviors of Ti bulk and Ti2O film can be described by the Bloch-Grüneisen formula, and the semiconducting behaviors of TiO1+d films in normal state and g-Ti3O5 film obey the variable range hopping and the small polaron hopping conduction mechanisms, respectively. For titanium monoxide TiO1+d (1.05 ≤ 1+d ≤ 1.17) films, increasing oxygen content is accompanied by an increase of disorder, a decrease of electron density of states at the Fermi level, and an enhancement of carrier localization, leading to a suppression of superconductivity.
关键词： Electron energy-loss spectroscopy,Oxygen content,Superconductivity,Transport properties,Titanium oxide thin films,Pulsed laser deposition
更新于2025-09-19 17:15:36
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Strain coupling and dynamic relaxation in multiferroic metal-organic framework [(CH3)2NH2][Mn(HCOO)3] with perovskite structure
摘要： Strain coupling with ferromagnetism and ferroelectricity plays an important role in the development of multiferroic metal-organic frameworks (MOFs) with strong magnetoelectric coupling, but the underlying mechanisms have not been well understood. Strain coupling and dynamic relaxation in multiferroic MOF with perovskite structure [(CH3)2NH2][Mn(HCOO)3] were investigated using X-ray diffraction (XRD), Raman spectroscopy, Infra-red (IR) spectroscopy, differential scanning calorimetry (DSC), magnetic measurements and dynamic mechanical analysis (DMA). DSC results showed peaks at 183 K and 190 K at the rate of 5 K/min during cooling and heating processes, respectively. Magnetic measurements showed magnetic transition at ~ 8.5 K at the heating rate of 2 K/min. Temperature and frequency dependences of elastic properties studied by DMA at frequencies of 0.5 Hz to 10 Hz between 140 K and 300 K at heating rate of 2 K/min indicated that the minimum in storage modulus and the maximum in loss modulus and loss factor occurred near 190 K. The peak height of loss modulus and loss factor decreased at higher frequency, and the peak temperature was independent of frequency, showing the features of first-order phase transition. Near 190 K, paraelectric to ferroelectric phase transition triggered by disorder–order transition of alkylammonium cations located in the framework cavities occurred accompanied by the structural phase transition from rhombohedral space group R c to monoclinic space group Cc. The elastic anomalies and large energy loss near 190 K were associated with the coupling of the local strain with the freezing of dimethylammonium cation and the freezing of twin walls.
关键词： Elastic modulus,Energy loss,Metal-organic framework (MOF),Phase transition,Dynamic mechanical analysis (DMA)
更新于2025-09-19 17:15:36
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Solar-Powered Artificial Photosynthesis Coupled with Organic Synthesis
摘要： Organic photovoltaics (OPVs) have attracted much attention because of the advantages in low-cost and large-area fabrication and the great potentials in achieving flexible and semi-transparent devices. However, compared with inorganic and perovskite solar cells, OPVs show relatively low photoelectric conversion efficiencies, which is admittedly attributed to intrinsically low dielectric constants of organic materials resulting in large energy losses. With the rapid development of fused-ring electron acceptors especially with an acceptor (A)-donor (D)-acceptor (A) arrangement, PCEs of OPV devices quickly surpassed 12% and even reached 16% in a very short period, in quite a few of which the Elosss are less than 0.6 eV. Although it is common for inorganic or perovskite solar cells, high-performance OPVs with the Elosss less than 0.5 eV are quite rare up to date, which means that the Eloss is still the key factor that limits the photovoltaic efficiency of the OPV technique. Nonetheless, progresses in the development of efficient OPVs by reducing the Eloss to less than 0.5 eV have been made in the past few years.
关键词： Photovoltaic efficiency,Energy loss,Organic solar cells,Non-fullerene acceptors
更新于2025-09-19 17:13:59
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Review on Recent Progress of All‐Inorganic Metal Halide Perovskites and Solar Cells
摘要： All-inorganic perovskites are considered to be one of the most appealing research hotspots in the field of perovskite photovoltaics in the past 3 years due to their superior thermal stability compared to their organic–inorganic hybrid counterparts. The power-conversion efficiency has reached 17.06% and the number of important publications is ever increasing. Here, the progress of inorganic perovskites is systematically highlighted, covering materials design, preparation of high-quality perovskite films, and avoidance of phase instabilities. Inorganic perovskites, nanocrystals, quantum dots, and lead-free compounds are discussed and the corresponding device performances are reviewed, which have been realized on both rigid and flexible substrates. Methods for stabilization of the cubic phase of low-bandgap inorganic perovskites are emphasized, which is a prerequisite for highly efficient and stable solar cells. In addition, energy loss mechanisms both in the bulk of the perovskite and at the interfaces of perovskite and charge selective layers are unraveled. Reported approaches to reduce these charge-carrier recombination losses are summarized and complemented by methods proposed from our side. Finally, the potential of inorganic perovskites as stable absorbers is assessed, which opens up new perspectives toward the commercialization of inorganic perovskite solar cells.
关键词： power conversion efficiency,solar cells,inorganic perovskites,stability,energy loss
更新于2025-09-19 17:13:59