Perovskite solar cells are limited by charge-recombination losses associated with trap-rich electron transport layers. However, the concentration-dependent role of waste-derived asphaltene in modifying interfacial structure and charge transport in mesoporous TiO₂ remains unresolved. Here we establish asphaltene as a functional modifier of mesoporous TiO₂ for improved perovskite photovoltaic performance. Perovskite solar cells incorporating mesoporous TiO₂ modified with 0–5 vol% asphaltene were fabricated and evaluated using structural, optical, charge-transfer, and photovoltaic measurements. Asphaltene produced denser perovskite films with larger grains, increasing the mean grain size from 0.554 μm for the reference to 1.49 μm at 2 vol%. The optimized 2 vol% device achieved a power conversion efficiency of 14.68%, compared with 10.60% for the reference, with a short-circuit current density of 23.01 mA cm⁻² and fill factor of 67.2%. After 800 h, the 2 vol% devices retained approximately 73% of their initial efficiency, compared with approximately 42% for the reference. These results demonstrate that asphaltene-mediated modification of mesoporous TiO₂ improves perovskite film formation, charge extraction, and photovoltaic performance. The approach opens the door to using an industrial hydrocarbon residue as a functional electron-transport-layer additive for lower-cost perovskite photovoltaics.
Negative differential resistance (NDR) accompanied by a simultaneous decrease in luminance was systematically investigated in multilayer organic light-emitting devices (OLEDs). 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (TPBi) and tris[2,4,6-trimethyl-3-(pyridin-3-yl)phenyl]borane (3TPYMB) were used as electron transport layers. The effects of transport-layer thickness, interfacial modification, and voltage-sweep conditions on the current density-voltage-luminance characteristics were examined to elucidate the origin of the NDR behavior. Pronounced NDR was observed at relatively high voltages together with a significant decrease in luminance, whereas hole-only and electron-only devices exhibited no NDR. The insertion of a thin LiF interlayer between TPBi and 3TPYMB completely eliminated the NDR, demonstrating the critical role of the TPBi/3TPYMB interface. The magnitude of the NDR strongly depended on the thicknesses of the TPBi and 3TPYMB layers. The NDR developed during the initial high-voltage sweep and disappeared in subsequent voltage sweeps. Based on these experimental results, an interfacial polarization model is proposed, in which holes accumulated at the EML/TPBi interface attract electrons to the TPBi/3TPYMB interface, where the electrons accumulate owing to the LUMO offset and are captured in interfacial trap states, acting as a fixed negative space charge. Together with the accumulated holes, the trapped electrons generate a reverse internal electric field that reduces the electric field in the 3TPYMB layer and suppresses carrier transport. The resulting suppression of carrier transport reduces electron-hole recombination, leading to simultaneous decreases in current density and luminance.
Nitroaromatics are widely used in the manufacturing process of explosives, organic dyes, insecticides or drugs and it poses great challenges concerning environmental monitoring, safety analysis and security check. Despite a variety of techniques including gas chromatography-mass spectrometry (GC-MS), Raman spectra or high-performance liquid chromatography (HPLC) are favorable for determining the analytes, the main obstacles during the on-site explosive detection involve the complex instrumentation, multiple operational steps and tedious procedures. Therefore, the development of portable and reliable device for in-field identification remains essential for the purpose of saving-cost and lowering the safety risks relevant to hazardous compounds. Herein, a lanthanide-based sensing platform based on terbium species entrapped electrospun fiber membrane is developed and it recognizes 2,4,6-trinitrophenol (TNP) effectively with diverse features including fast response rate (30 s), reliability, lower detection limit (3.17 ppm) and resistance to interference. Its high reversibility is observable by fifty cycles of immersion in TNP/EtOH solution. The emission quenching process is predominantly governed by the inner filter effect (IFE) and minor proportion from photoinduced electron transfer (PET). The representative contribution is to assemble a portable detection device which integrates light source, optical path and signal collection module into an independent unit (Length: 98 mm; Width: 65 mm; Height: 33 mm; Weight: 105 g). The miniaturized instrument realizes rapid response to TNP and it is suitable for on-site determination of analytes.
Developing agglomeration-free, stable Pt-based bimetallic nanostructures on conductive substrates is essential for achieving high-performance electrochemical sensing. Here, a Pt–Cu bimetallic nanoparticle-decorated reduced graphene oxide (Pt–Cu/rGO) nanocomposite is drop-casted on a glassy carbon electrode for the electrochemical detection of rutin with highly sensitive and selectively. A sustainable chemical reduction technique was used to fabricate the Pt–Cu/rGO nanocomposite, which was then thoroughly examined using transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The Pt-Cu/rGO/GCE sensor has an ultralow detection limit of 0.0019 µM and a broad linear response range (0.005–2.2 µM) outperforming monometallic equivalent sensors and many alternative sensor designs. This is a consequence of the improved electron-transfer kinetics toward rutin oxidation and enhanced electric conductivity resulting from the synergistic interaction between Pt–Cu nanoparticles and rGO. Furthermore, accurate rutin detection and quantification in real samples, specifically apple juice and green tea, confirms the Pt-Cu/rGO/GCE sensor's appropriateness for routine food analysis and further demonstrates its practical application.
The accurate and rapid detection of nitrogen dioxide (NO2) at room temperature remains a critical challenge for environmental monitoring and protection of human health. In this study, the layered gas-sensitive composites based on polyaniline (PANI) and chemically modified multi-walled carbon nanotubes (MWCNTs) have been developed. The layer-by-layer deposition technique was employed to fabricate 3-, 5-, and 7-layer PANI/MWCNT films. It has been found that the introduction of PANI significantly alters the sensing behavior, with the effect being highly dependent on the number of layers. The highest response (22.0% at 2 ppm NO2) was achieved for the 3-layer configuration of PANI/MWCNTs, while further layering led to a decline due to physical blockage of adsorption sites. To complement the experimental findings, a deep neural network (DNN) model was developed to predict sensor responses, achieving high accuracy (test R² of 0.9680–0.9997) across all configurations. SHapley Additive exPlanations (SHAP) analysis was further employed to interpret the model predictions, revealing that NO2 concentration and time are the most influential features and that the 3-layer PANI/MWCNT sensor exhibits the highest sensitivity and widest SHAP value range. Experiments identify the optimal layered architecture of the sensor, and the DNN algorithm complements this by accurately modelling and interpreting the NO₂ sensing response, offering a promising pathway for the rational design of high-performance NO₂ sensors.
