Transient electroluminescence (TrEL) is widely employed to uncover the charge carrier and exciton properties of various light-emitting diodes (LEDs). The TrEL testing has to meet some basic criteria in order to guarantee the comparability and reliability of results across various research teams or laboratories. However, a frequent testing error arises when the TrEL test exceeds its linear dynamic range (LDR) of the photodetectors, compromising the reliability of the output signal and ultimately yielding inaccurate conclusions. In this work, various anomalous TrEL features that result from non-LDR conditions were revealed. By analyzing those features, three key guidelines for LDR examination in TrEL studies were summarized: 1) always check whether varying the pulse period and pulse width changes the TrEL response, since such variation may indicate that the PMT is operating beyond the LDR and should be treated as an initial warning sign; 2) always check whether a high photomultiplier tubes (PMTs) gain setting causes saturation, which can be verified by comparing with low-gain results: TrEL intensity changes but waveform shape remains unchanged; 3) always check whether the maximum output current of the photodetector remains within the LDR. These guidelines provide a preliminary validation procedure to rule out detector-induced artifacts before attributing TrEL characteristics to device-intrinsic processes, thereby improving the reliability of TrEL analysis in various LEDs.
Optimizing the interlayer interface is critical for increasing the efficiency of planar perovskite solar cells (PSCs). Interlayer design is considered to be a promising method. This study makes use of the structural features of methyl 3-amino-6-chloro-2-pyrazinecarboxylate (MAPC), where the acidification treatment deeply activates its functional groups, improving electron transport capacities between the electron transport layer and the perovskite layer to improve the device performance. MAPC molecules have been protonated and attached onto the TiO2 surface via electrostatic interactions to establish hydrogen bonds with the perovskite layer to modify the interface of TiO2/perovskite. The device efficiency increases from 19.52% to 21.78% as a result of the interface passivation. This study improves the functional group interactions of passivation materials via acid treatment. Furthermore, PSCs deposited on TiO2/MAPCH demonstrate increased stability. Unencapsulated PSCs retain about 75% of their original PCE after aging for 720 hours under ambient conditions compared to 65% for the control devices.
Finely controlling the active layer morphology is the core element for maximizing the photovoltaic performance of organic solar cells (OSCs), particularly for systems based on non-fullerene acceptors. While thermal annealing efficiently optimizes morphology, its heat requirement increases manufacturing complexity and restricts broader flexible substrate compatibility. Although solvent annealing is a promising heat-free alternative, the utilization of weakly polar solvent vapors and their underlying micro-structural evolution remain largely unexplored. Herein, a room-temperature weakly polar solvent annealing strategy is proposed, utilizing film-depth-dependent light absorption spectroscopy (FLAS) to systematically monitor the vertical morphology evolution in PM6:Y6-based inverted OSCs. We demonstrate that while excessive solvent exposure inevitably leads to detrimental macro-aggregation and structural defects, a precisely controlled room-temperature solvent treatment effectively fine-tunes the molecular packing and micro-morphology. An optimal 3-min chloroform (CF) vapor annealing induces an ideal vertical phase separation and high domain purity, which perfectly matches the charge extraction requirements of the inverted architecture. Consequently, without any thermal input, the optimized devices achieve exciton dissociation and charge collection efficiencies highly comparable to those of thermally annealed devices, delivering a competitive power conversion efficiency (PCE) of 15.0%. Furthermore, benefiting from this completely heat-free process, the fabricated flexible OSCs avoid substrate deformation and achieve an impressive PCE of 13.7%. Ultimately, this study demonstrates that precisely controlled weakly polar solvent vapor annealing provides a robust strategy for manufacturing high-performance, low-temperature rigid and flexible non-fullerene organic photovoltaics.
Achieving low-voltage operation in organic thin-film transistors (OTFTs) remains a primary challenge for wearable electronics. Here, low threshold voltage poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]-thiophene)] (DPPDTT) OTFTs using ultrathin aluminium oxide (AlxOy) as the gate dielectric are reported. Reducing the AlxOy thickness from 5 to 3 nm does not inherently improve the transistor performance. Modifying the 3 nm AlxOy with self-assembled monolayers (SAMs) usually used for alumina surface treatment increases field-effect mobility but does not appreciably enhance other important device parameters. To address this, a polymer semiconductor/dielectric blend consisting of DPPDTT (semiconductor) and poly(methylmethacrylate) (PMMA) (dielectric) has been applied. An optimized blend on 3 nm AlxOy yields DPPDTT OTFTs operating at the gate voltage |VG| ≤ 2 V with the field-effect mobility (μ) of ∼0.06 cm2 V−1 s−1, threshold voltage |VT| below 1 V, subthreshold swing (SS) around 100 mV/dec, and on/off current ratio (Ion/Ioff) in excess of 5 × 104. These results demonstrate that polymer blending may provide a more robust interface passivation than application of SAMs, which is particularly important for OTFTs using ultrathin metal oxide dielectrics.
Wide-bandgap perovskite solar cells have shown great potential in tandem photovoltaic applications; however, insufficient interfacial charge transport remains a key bottleneck limiting further efficiency improvements. In this work, NiOx hole transport layers with different thicknesses were prepared by tuning the precursor concentration, and their effects on interfacial properties and device performance were systematically investigated. The results show that increasing NiOx thickness leads to a higher work function and improved surface wettability, which facilitates more uniform spreading and nucleation of the perovskite precursor, resulting in smoother perovskite films with larger grain sizes. Steady-state photoluminescence measurements indicate that the film prepared at an intermediate concentration exhibits the most efficient interfacial charge extraction. Consequently, the device performance shows a pronounced thickness dependence, with the 5 mg mL-1 device achieving the best power conversion efficiency (PCE) of 19.41%. These results demonstrate that simple thickness modulation enables synergistic optimization of NiOx interfacial properties, providing an effective strategy for interface engineering in wide-bandgap perovskite solar cells.
Achieving efficient and narrowband deep-blue emission remains a persistent challenge for multiple-resonance thermally activated delayed fluorescence (MR-TADF) materials, which are essential for high-definition organic light-emitting diode (OLED) displays. Here, we present a synergistic backbone-donor engineering strategy that transforms a simple mono-boron B/N/O framework into an efficient deep-blue emitter with high spectral sharpness. By synergistically integrating an auxiliary donor, 10-phenyl 5H-phenophosphazinine 10-sulfide (NPS) and rigid carbazole-fused motif within the MR backbone, this synergistic modification simultaneously accelerates reverse intersystem crossing and suppresses specific medium-to-high frequency molecular vibrations that contribute to spectral broadening by steric hindrance traction effects, enabling efficient triplet harvesting and significant narrowband emission. The suppressed molecular vibrations yield a small full-width-at-half-maximum (FWHM) of only 18 nm at 444 nm in toluene. The OLEDs based on proof-of-concept achieve an external quantum efficiency (EQE) of 32.9% with deep-blue CIEy coordinate of 0.067, retaining high efficiencies of 25.1% and 16.6% at 100 and 1000 cd m- 2, respectively. This work represents a significant step toward addressing the longstanding trade-off between efficiency and color purity in deep-blue MR-TADF systems, offering a versatile molecular design principle for next-generation display and lighting technologies.
Organic semiconductor lasers (OSLs) remain challenging due to triplet-induced optical losses, such as singlet-triplet annihilation and triplet excited-state absorption, which become prominent at high exciton densities and increase the lasing threshold. In this study, we investigate a novel bifunctional molecule, BOXDP3, which incorporates an anthracene dimer unit into a benzobisoxazole derivative with a low amplified spontaneous emission (ASE) threshold. BOXDP3 exhibits a low ASE threshold of 3.8 mu J cm-2 in a 2 wt% CBP-doped film, representing a significant reduction compared to previously reported anthracene derivatives. Furthermore, through concentration-dependent triplet-triplet upconversion (TTU) threshold analysis in triplet-sensitized solutions, we provide evidence of intramolecular TTU activity in BOXDP3. In 0.5 wt% doped CBP thin films, longlived delayed fluorescence exceeding 100 mu s is observed, originating from triplet-to-singlet recycling via intramolecular TTU. These results indicate that incorporating intramolecular TTU functionality into laser materials would be an effective strategy for realizing next-generation, low-threshold, and stable organic semiconductor lasers.
We compare organic light-emitting diode (OLED) performance in devices based on MQAB emitters doped into similar electron transporting molecular hosts, TBADN (2-tert-butyl-9,10-di(naphtha-2-yl) anthracene) and PADN (2-phenyl-9,10-di(naphtha-2-yl) anthracene), the former exhibiting spontaneous polarization due to molecular orientation (SOP) while the latter does not. We quantify the host electric polarization and find that the device efficiency is lower when using the more polarized TBADN. Using charge modulation spectroscopy, we infer the root cause to be quenching of the luminescent excited state by cations that accumulate in the hole transport layer at the emissive interface. The cation accumulation is caused by interfacial charges associated with the SOP and persists even under conditions where the OLED emits light.
Organic solar cells (OSCs) have attracted significant research interest as next-generation photovoltaic technologies due to their environmental friendliness, lightweight nature, and flexibility. However, the performance of OSCs exhibits notable sensitivity to variations in incident light angle, which restricts their practical application under real-world illumination conditions to some extent. In this paper, a microstructure film composed of polystyrene (PS) and poly (methyl methacrylate) (PMMA) was fabricated on the back side of the device via a straightforward spin-coating process to reduce angular dependence of OSCs' efficiency on incident light. At an optimal blending ratio of 3:7, a trench-like microstructure forms, enhancing internal light reflection and extending the optical path length. Consequently, the short-circuit current density increases from 25.54 mA/cm2 to 26.47 mA/cm2, and the power conversion efficiency improves from 14.08% to 14.77% under normal incidence. More importantly, the device retains 94.1% of its initial efficiency at an oblique incident angle of 45 degrees, demonstrating excellent angular independence. This research presents a promising approach for reducing the angular dependence of OSCs' performance on incident light, which is expected to facilitate their wider adoption in practical industrial applications.
The performance of organic electronic devices is closely tied to their nanoscale donor-acceptor microstructure, yet quantifying these features remains challenging using conventional characterization tools. X-ray scattering and electron microscopy techniques provide high-fidelity structural information, but they are slow, expensive, and challenging to deploy in high-throughput or autonomous processing environments. Here, we propose a complementary, proxy-based route to microstructure inference that leverages the device's transient short-circuit current response under modulated illumination. Using a microstructure-aware excitonic drift-diffusion (EDD) framework that incorporates arbitrary time-dependent generation profiles, we compute current (J(t)) responses for 500 computationally generated donor-acceptor morphologies subjected to full-wave-rectified sinusoidal excitation. From each response, we extract a suite of physically motivated time-and frequency-domain features and pair them with key microstructural descriptors, specifically interfacial area, characteristic domain size, and connectivity. SHAP-based feature selection reveals that a compact subset of transient-response features captures most of the microstructure dependence. Linear surrogate models trained on these subsets achieve good test R2 across all descriptors, with interfacial area and domain-size predictions exceeding R2 = 0.9, using fewer than 10% of the simulated morphologies for training. These results demonstrate that high-frequency, amplitude-modulated electrical measurements can recover essential microstructural fingerprints, suggesting a pathway toward compact, non-destructive, and automation-ready characterization tools for high-throughput research in organic electronics.
This study presents an antisolvent-free, one-step spin-coating method for fabricating {CH(NH 2 ) 2 } 1-x Cs x PbI 3 (FA 1x Cs x PbI 3 ) perovskite films using a volatility-controlled cosolvent. Using 2-Methoxyethanol (2-ME) as a highly volatile primary solvent to drive rapid supersaturation, while 1-cyclohexyl-2-pyrrolidone (CHP) acts as a highboiling-point cosolvent to moderate crystallization kinetics through intermediate stabilization. Crucially, CsCl is introduced as a strategic additive to overcome the inherent low solubility of conventional cesium precursors in 2-ME. CsCl appears to play dual roles: enabling effective Cs + incorporation to stabilize the alpha-phase perovskite and likely assisting crystallization by facilitating the formation of transient chloride-mediated intermediates. Optimizing the formulation with 3.5 vol% CHP and 7.5 mol% CsCl led to significant improvements in film uniformity, crystallinity, and optical properties. Consequently, n-i-p planar heterojunction solar cells fabricated using a 0.45 M precursor solution achieved a high power conversion efficiency of 21.1% with short-circuit current density (25.8 mA/cm 2 ), open-circuit voltage (1.06 V), and fill factor (77.5%), and a stabilized output of 20.8%, confirming the potential of this DMF- and antisolvent-free process for scalable PSC production, while emphasizing that the present approach is based on volatility control rather than complete solvent detoxification.
Near-infrared (NIR) absorbing and/or emitting organic materials are increasingly important for next-generation optoelectronic devices. Narrow-gap push-pull conjugated polymers have gained particular attention in this respect because of their tunable optical properties and promising performance in (semitransparent) organic photovoltaics and NIR photodetectors. In this study, three novel diketopyrrolopyrrole (DPP) based narrow-gap donor polymers containing fluorine-, chlorine-, or nitrile-substituted thiophene units are rationally designed and synthesized with the aim of enhancing the open-circuit voltage in NIR-active (semitransparent) organic solar cells. The P-DPP-3T(F):Y6 blend affords a power conversion efficiency of 5.2%, surpassing the P-DPP-3T:Y6 reference combination (yielding 4.5%). Further optimization with other NIR-absorbing non-fullerene acceptors gives an enhanced solar cell efficiency of 6.6% for the P-DPP-3T(F):Y16F combination, and even 7.8% for P-DPP-3T:Y16F. When utilized with a semitransparent top electrode, the latter affords an efficiency of 5.0% with an average visible transmittance of 33%.
Flexible piezoelectric poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), which has a favorable acoustic impedance matching character with water, is an ideal candidate for designing a piezoelectric hydroacoustic transducer (PHT). In this work, the P(VDF-TrFE) sheet with a considerable piezoelectric constant (-46 pC/N) is used as the functional layer, supplemented by different matching and backing layers, and four various PHTs are fabricated. The influence of structural characteristics of P(VDF-TrFE) sheet on the frequency-domain response, receiving sensitivity, and other electroacoustic properties is revealed through finite element analysis (FEA) and experimental verification. A single-factor FEA and experimental study show that the PHT based on a 1 mm-thick P(VDF-TrFE) sheet shows a higher receiving sensitivity (-181.3 dB re 1 V/mu Pa) than that of other thicknesses. Moreover, the hydroacoustic performance of four PHTs with different structural configurations is evaluated through underwater testing, indicating that the backing layer weakened the interference signal, and the matching layer improved the transfer efficiency of sound energy. More interestingly, temperature stability and sonar experiments prove that PHT with a backing layer has the best comprehensive performance and practical applicability, exhibiting the great application potential of P(VDF-TrFE)-based receiving-type PHT for ocean exploration.
Quantum dot (QD) inks incorporating scattering particles offer great potential for high-performance color conversion layers with high color purity and wide color gamut. Electrohydrodynamic (EHD) printing enables high-resolution additive manufacturing but is limited by the lack of suitable scattering inks. Here, we systematically optimized a QD ink system by mixing TiO2 scattering particles for color conversion applications. The dispersion stability and continuous inkjet behavior of TiO2 particles were investigated, revealing that low-boiling-point solvents lead to rapid evaporation and nozzle clogging. Isobornyl methacrylate (IBOMA) with high boiling point was therefore selected as the solvent. Optical characterization shows that the ink containing 4 wt% TiO2 achieves a blue-light absorption of 84.3% and a color conversion efficiency (CCE) of 11.4%, approximately 40% higher than that of pure QD ink, without noticeable aggregation over three days period. For the first time, EHD printing was successfully used to fabricate scattering-particle-doped QD color conversion patterns with pixel sizes of similar to 30 mu m, demonstrating the feasibility of scattering inks for high-resolution micro-LED color conversion.
Organic semiconductor nanoparticles-based electronic devices have sparked considerable interest as their manufacturing process allows the use of non-toxic solvents. However, the development of microfabrication techniques to pattern semiconductor nanoparticle film with benign solvent fell behind. Here, we demonstrate a simple and low-cost microfabrication process, where the patterning is done by solution-stamping of alcohol-soluble polymer and subsequent lift-off of semiconductor nanoparticles. To demonstrate the potential of the developed process, aligned solution-stamping was used to pattern different function layers of nanoparticle-based organic thin film transistors.
Pyrene has emerged as a key scaffold in the design of organic semiconductors, distinguished by its inherent propensity for aggregation, ease of functionalization, and capacity for robust pi-stacking interactions. However, the exploration and application of pyrene-based scaffolds in n-type semiconductors remain relatively scarce. To address this challenge, three novel pyrene-derived semiconductors functionalized with pentafluorophenyl (5 F) end-groups were synthesized and characterized in organic field-effect transistors (OFETs). Compared to the pyrene-core analogue (1,6-5FPy), the 4,9-diazapyrene (PyNN) -core derivatives (1,6-5FPyNN and 3,8-5FPyNN) exhibit deeper lowest unoccupied molecular orbital (LUMO) energy levels and enhanced electron transport properties, attributed to the incorporation of two nitrogen atoms into the pyrene framework. Through this synergistic modulation by N atoms doping and substitution site isomerism, the three molecules exhibit distinct conformation and packing motifs in the single crystals. Specifically, 1,6-5FPyNN possesses a reduced intramolecular torsion angle and strengthened intermolecular interactions, evidenced by short C-H & centerdot;& centerdot;& centerdot;N contacts (2.47 & Aring;). The molecules adopt an edge-on orientation on the substrate surface, and the polycrystalline films display elongated, interconnected grains (similar to 2 mu m), which is favourable for charge transport. The n-type small-molecule semiconductor 1,6-5FPyNN demonstrates optimal performance, achieving an electron mobility of 1.64 +/- 0.29 cm(2) V-1 s(-1), establishing this material as one of the most promising n-type small-molecule pyrene derivatives reported thus far.
