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Molecular engineering of a conjugated polymer as a hole transporting layer for versatile p–i–n perovskite solar cells
摘要： Along with the development of perovskite materials, which have enormous potential for optoelectronics such as solar cells and light-emitting diode devices, numerous organic semiconductor polymers, which have been critically adopted into the hole and electron transporting layers, have been synthesized and studied. In neiep-structured perovskite solar cells, various outstanding polymer materials have been successfully applied. However, in peien-structured solar cells, the hydrophobic nature of the polymers makes the sequential deposition of a perovskite thin ?lm dif?cult. Several destructive methods have been proposed; however, a more ef?cacious and fundamental method is urgently needed. Here, we present a nondestructive polymer hole-transporting layer (HTL) thin-?lm formation process based on molecular engineering via a simple solvent process. When we used various solvents with different volatilities, perovskite ?lm formation was achieved on polymer thin ?lms formed from highly volatile solvents. In addition, we elucidated the structure and orientation of the molecules in the ?lms and revealed that the molecular structure of face-on orientation for the horizontally aligned hydrophobic alkyl groups induced a lower surface energy of the ?lm, as determined by grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements. Furthermore, the tilt angle of the molecules, which was calculated from the results of quantitative near-edge X-ray absorption ?ne structure (NEXAFS) analysis, was found to correlate with the surface energy. This result provides guidance for polymer-orientation and surface-energy studies, and perovskite solar cells fabricated using the polymer HTL demonstrated good durability and ?exibility. We expect that our approach represents a new route for fabricating peien-structured solar cells and that numerous valuable p-type conjugated polymers will be developed via our proposed molecular engineering process.
关键词： Solvent process,Organic semiconductor,Flexible device,Conjugated polymer,Perovskite solar cell,Molecular engineering
更新于2025-09-19 17:13:59
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Enhanced performance of ternary organic solar cells with a wide bandgap acceptor as the third component
摘要： Two n-type organic semiconductor (n-OS) acceptors, C8-SF and Y-MODF, were designed and synthesized for application in organic solar cells (OSCs). C8-SF shows a lower lowest unoccupied molecular orbital (LUMO) energy level and lower bandgap with an absorption edge at 822 nm. Y-MODF possesses a relatively larger bandgap and higher LUMO and lower HOMO (highest occupied molecular orbital) energy levels than C8-SF. With the polymer PM6 as the donor, the OSC with C8-SF as the acceptor delivers a power conversion efficiency (PCE) of 11.59% with a lower open circuit voltage (Voc) of 0.787 V, while the device with Y-MODF as the acceptor exhibits a lower PCE of 8.63% but a higher Voc of 0.984 V benefiting from the higher LUMO of the Y-MODF acceptor. Then, a series of ternary OSCs were fabricated with PM6:C8-SF as the host system and Y-MODF as a third component. The optimal ternary OSCs with 25% Y-MODF incorporated into the acceptor achieve a higher PCE of 13.39%, with an improved Voc of 0.845 V, a Jsc of 20.88 mA cm?2 and a FF of 75.87%. It was found that adding Y-MODF to the PM6:C8-SF binary system suppressed monomolecular recombination and improved the utilization of 450–600 nm range photons. Molecular packing is further optimized with more balanced hole and electron transport, thus resulting in the enhanced Jsc and FF for the ternary OSCs. These results indicate that the addition of a wide bandgap acceptor with a higher LUMO energy level to a binary donor/acceptor system may have potential for Voc and PCE improvement of ternary OSCs.
关键词： ternary OSCs,n-type organic semiconductor,organic solar cells,open circuit voltage,power conversion efficiency
更新于2025-09-16 10:30:52
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Study the Nonlinearity Characteristics of Organic-Semiconductor (CuPc) Prepared Via Pulsed Laser Deposition Technique with Different Thickness
摘要： The optical absorption spectrum, Photoluminesces, and non-linear optical properties for Copper Phthalocyanine (CuPc) thin films (150,300 and 450 nm) respectively have been investigated via pulsed laser deposition technique. The absorption spectrum indicted that there are two bands one in UV around 330 nm which called B-band and the second in Visible around 650nm which called Q-band. Photoluminescence spectrum related to deposit samples has been determined with different thicknesses. From closed and open aperture Z-scan data non-linear absorption coefficient and non-linear refractive index have been calculated respectively using He-Ne laser which have beam waist of (24.2 μm), wave-length of (632.8 nm) and Rayleigh thickness was 2.9 mm. Through dividing closed by open apertures, non-linear refractive index was calculated accurately. Finally, the study also showed the suitability of the deposited films as an optical limiter at the wavelength 632.8 nm.
关键词： Copper Phthalocyanine,Organic Semiconductor,Non-linear properties,Pulsed laser deposition
更新于2025-09-16 10:30:52
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Unraveling the Structure-Property Relationship of Molecular Hole Transporting Materials for Perovskite Solar Cells
摘要： Clarifying the structural basis and microscopic mechanism lying behind electronic properties of molecular semiconductors is of paramount importance in further materials design to enhance the performance of perovskite solar cells. In this paper, three conjugated quasi-linear segments of 9,9-dimethyl-9H-fluorene, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and 2,6-diphenyldithieno[3,2-b:2',3'-d]thiophene are end-capped with two bis(4-methoxyphenyl)amino groups for structurally simple molecular semiconductors Z1, Z2, and Z3, which crystalline in the monoclinic, triclinic, and monoclinic space groups, respectively. The modes and energies of intermolecular noncovalent interactions in various closely packed dimers extracted from single crystals are computed based on the quantum theory of atoms in molecules and energy decomposition analysis. Transfer integrals, reorganization energies, and center-of-mass distances in these dimers as well as band structures of single crystals are also calculated to define the theoretical limit of hole transport and microscopic transport pictures. Joint X-ray diffraction and space-charge limiting current measurements on solution-deposited films suggest the dominant role of crystallinity in thin film hole mobility. Photoelectron spectroscopy and photoluminescence measurements show that an enhanced interfacial interaction between perovskite and Z3 could attenuate the adverse impact of reducing the energetic driving force of hole extraction. Our comparative studies show that molecular semiconductor Z3 with a properly aligned HOMO energy level and a high thin film mobility can be employed for efficient perovskite solar cells, achieving a good power conversion efficiency of 20.84%, which is even higher than that of 20.42% for spiro-OMeTAD control.
关键词： charge recombination,perovskite solar cell,molecular crystal,noncovalent interaction,crystallinity,charge transport,organic semiconductor
更新于2025-09-16 10:30:52
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D‐A Type Pendant Conjugated Molecules based on Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers
摘要： A set of fluorene-capped pendant conjugated molecules (T-m and T-p), which consist of triazine center with three carbazole substituents as the donor-acceptor (D-A) type pendant structure, were designed, synthesized and investigated as gain media for organic semiconductor lasers (OSLs). Particularly, varying the capping positions of the fluorene units onto the pendant core structures results in obviously different intramolecular charge transfer (ICT) properties, whereas T-m manifested depressed ICT characteristic and high fluorescence quantum yield. The lowest ASE threshold in neat films was recorded of 1.9 μJ/cm2 for T-m and 83.8 μJ/cm2 for T-p, respectively, which indicated that depressed ICT characteristic in the case of T-m helps to enhance the ASE properties. Remarkably, the ASE threshold remained almost unchanged and the ASE spectra showed very small shifts (within 1 nm) for T-m with film samples annealed up to 180°C in open air. In contrast, its linear counterpart 2FEtCz-m showed obviously increased ASE threshold upon annealing above 100°C. The results suggest that the selective construction of conjugated pendant molecules with depressed ICT characteristics is beneficial for finely modulating the optical and electrical properties as well as improving the thermostability and photostability, which manifests the great potentials as robust gain media for OSLs.
关键词： Organic semiconductors,Amplified spontaneous emission (ASE),Organic semiconductor lasers,Pendant conjugated molecules,Intramolecular charge transfer (ICT)
更新于2025-09-12 10:27:22
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Photocurrent deviation from linearity in an organic photodetector due to limited hole transport layer conductivity
摘要： It has been demonstrated that p-doped polymer layers are a convenient replacement as hole transport layer (HTL) for the widely used Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), yielding comparable photodetection performances at low light intensities. In this work, we aim to evaluate the response of organic photodetectors (OPDs) with increasing light intensity when p-doped PBDTTT-c is used as HTL. Photocurrent linearity measurements are performed on devices processed with both PEDOT:PSS and p-doped PBDTTT-c to better determine the role of the HTL. We show a deviation of the photocurrent from linearity for light intensities above 10?3 W/cm2 at 0 V applied bias due to distinct mechanisms depending on the HTL material. While space charge limited photocurrent (SCLP) explains the non-linearity at high light intensity for the device processed with PEDOT:PSS, bimolecular recombination is responsible for the loss in linearity when p-doped PBDTTT-c is used as HTL. The replacement of PEDOT:PSS by p-doped PBDTTT-c, which is 6 orders of magnitude less conductive, induces Langevin recombination, causing photocurrent non-linearity. Therefore, this study emphasizes the need for highly conductive transport layers when photodetection applications are targeted, and motivates further improvements in organic semiconductor doping.
关键词： Photocurrent linearity,Organic semiconductor doping,Organic photodetectors
更新于2025-09-12 10:27:22
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Improved organic solar cell by incorporating silver nanoparticles embedded polyaniline as buffer layer
摘要： The role of silver nanoparticles (AgNP) in polyaniline (PANI) as a buffer layer for ITO/AgNP-PANI/PANI/Al solar cell was investigated. It is observed that AgNP-PANI buffer layer significantly improves the electrical parameters such as diode-ideality factor, series-resistance, energy-barrier height, and shunt-resistance as a growing function of AgNP concentration. On-the-other hand oppose to the dark current-voltage response, 0.5% concentration of AgNP in buffer layer shows the most optimum photovoltaic response and cause to increase the power conversion efficiency (PCE) nearly 5 times compared to same solar cell without buffer layer. Such improvements in electrical parameters can be interpreted as the reduction in interfacial trap states as well as enhancement in interfacial dipole-moment by AgNP embedded buffer layer for given photovoltaic device. While, the observed optimum photovoltaic behavior at 0.5% AgNP concentration is may be due to the trade-offs between gains and losses for optical absorption enhancement, self-absorption heating and interface recombination losses respectively. It is also observed that the AgNP embedded PANI buffer layer approach is an effective solution to lower the photovoltaic degradation and hence improves the stability of the photovoltaic devices.
关键词： ITO,Silver nanoparticles,Solar cell,Organic semiconductor,Organic electronics,Polyaniline,Buffer layer
更新于2025-09-12 10:27:22
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Mobility of charge carriers in self-assembled monolayers
摘要： We present a new approach to study charge transport within 2D layers of organic semi-conductors (OSCs) using atomic force microscopy (AFM)-based lithography applied to self-assembled monolayers (SAMs), fabricated from appropriate organothiols. The extent of lateral charge transport was investigated by insulating pre-defined patches within OSC-based SAMs with regions of insulating SAM made from large band gap alkanethiolates. The new method is demonstrated using a phenyl-linked anthracenethiolate (PAT), 4-(anthracene-2-ylethynyl)benzyl thiolate. I–V characteristics of differently shaped PAT-islands were measured using the AFM tip as a top electrode. We were able to determine a relationship between island size and electrical conductivity, and from this dependence, we could obtain information on the lateral charge transport and charge carrier mobility within the thin OSC layers. Our study demonstrates that AFM nanografting of appropriately functionalized OSC molecules provides a suitable method to determine intrinsic mobilities of charge carriers in OSC thin films. In particular, this method is rather insensitive with regard to influence of grain boundaries and other defects, which hamper the application of conventional methods for the determination of mobilities in macroscopic samples.
关键词： organic semiconductor,self-assembled monolayer,lateral charge transport,nanografting,conducting atomic force microscopy
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Fluorescence-Based Sensors and Preconcentration Techniques for Buried Explosives Detection
摘要： Trace detection of explosives is an important challenge in both humanitarian landmine clearance and in homeland security scenarios. The ability to detect the presence of explosives across an area of interest would be of particular use in technical surveys of suspected minefields. In this paper we present the development and application of fluorescence-based trace-explosives sensors based on organic semiconductor thin films. We show that these can be used to detect nano-gram level quantities of nitroaromatic (TNT-like) molecules, and combine them for the first time with a novel preconcentration approach to detect buried explosives. Initial field trials on a test minefield will also be presented, in which the sensors are used to detect trace explosives collected by colonies of foraging honeybees.
关键词： fluorescence-based sensors,nitroaromatic molecules,buried explosives detection,organic semiconductor thin films,preconcentration techniques
更新于2025-09-12 10:27:22
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A computational approach to study the optoelectronic properties of F-BODIPY derivatives at the bulk level for photovoltaic applications
摘要： The Dipyrrin compounds are recognized as imminent and hi-tech organic semiconductor materials (OSMs) designed for photovoltaic applications owing to low-cost, flexible, and eco-friendly nature. In a latest study, several optoelectronic properties of conjugated F-BODIPY derivatives were studied by using the density functional theory (DFT) at (GGA/PBE) level. This analysis classifies Comp_1 (5,5-difluoro-1,37,9-tetramethyloctahydro-1H,5H-5l4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinine) as a direct band-gap semiconductor with a band-gap of 2.81 eV. The band-gap of Comp_2 (2-ethyl-5,5-difluoro-1,3,7,9-tetramethyloctahydro-1H,5H-5l4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinine) and Comp_3 (2,8-diethyl-5,5-difluoro-1,3,7,9-tetramethyloctahydro-1H,5H-5l4-dipyrrolo[1,2-c:2',1'-f] [1,3,2] diazaborinine) are reduced by 1.25 and 1.09 eV, respectively in comparison with parent molecule Comp_1 owing to the influence of p- orbitals of all atoms in crystal structures. The reduction in energy and density of states (DOS) for these compounds in this study validated that band-gap could be improved to a required value for optoelectronic applications by derivatives modeling. Additionally, optoelectronic properties at the solid-state bulk level were also computed. Several features of interest at solid-state bulk level exposed the F-BODIPY derivatives as competent compounds for organic semiconductor devices applications.
关键词： Bandgap,Bulk level,Photovoltaic application,F-BODIPYs,Organic semiconductor
更新于2025-09-12 10:27:22