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Dual Functions of Crystallization Control and Defect Passivation Enabled by an Ionic Compensation Strategy for Stable and High-Efficient Perovskite Solar Cells
摘要： The fabrication of perovskite films with high crystallization quality, less defects and fewer grain boundaries (uncoordinated ions), is one critical step to obtain excellent power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). In this work, we develop a novel method to control the perovskite growth toward better crystallinity and less defects using I- and thiourea as additives for the first time (we define ITU for I- and thiourea). Grain boundaries in the perovskite films are significantly reduced compared with the traditional method. Moreover, concentration of the defects in perovskite films is decreased by nearly one-half. Based on high-quality films, the PSCs with a champion PCE of 20.39% present a stabilized output efficiency of 19.26% under one sun illumination compared with that of the control devices (17.75%). The devices also exhibit small hysteresis and excellent long-term and light stability. The devices can retain 80% of the initial PCE after 100 h of light soaking or 30 days of aging in ambient atmosphere. This work not only demonstrates a novel approach to passivate the defects by balancing iodide ions, but also offers a strategy to control the perovskite film growth, which can be widely used in photoelectric devices.
关键词： iodide ions,crystallinity,defect states,perovskite solar cells,light stability
更新于2025-09-12 10:27:22
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Characterisation of UHMWPE Polymer Powder for Laser Sintering
摘要： Ultra-high molecular weight polyethylene (UHMWPE) is a thermoplastic semicrystalline polymer that has outstanding mechanical properties, low friction coe?cient, excellent wear resistance, and is highly resistant to corrosive chemicals. UHMWPE is found in many applications including arti?cial joints and ?ltration. However, UHMWPE parts cannot be produced easily by traditional techniques, such as injection moulding and extrusion because of its very high melt viscosity owing to the extremely long polymer chains. Few attempts were made to process UHMWPE by additive manufacturing, particularly laser sintering. This is due to the lack of understanding of the powder properties of UHMWPE. Therefore, the aim of the powder characterisation process in this study is to gain a better understanding of the material requirements and provide a detailed insight on whether UHMWPE is a suitable material for laser sintering. The characterisation process includes powder morphological and ?ow characteristics, thermal behaviour and stability, and crystallinity of UHMWPE. The study reveals that the sintering behaviour of polymers is controlled by the morphology of the particles in addition to the viscous ?ow of UHMWPE. There are still di?culties of processing UHMWPE due to highly agglomerated structure of smaller particles with the presence of ?brils in the UHMWPE particles.
关键词： powder ?ow,crystallinity,laser sintering,hot stage,UHMWPE
更新于2025-09-11 14:15:04
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Rapid Diagnosis Of Drug Agglomeration And Crystallinity In Pharmaceutical Preparations By Electrospray Laser Desorption Ionization Mass Spectrometry Imaging
摘要： In this study we evaluate the applicability of electrospray laser desorption ionization mass spectrometry imaging (ELDI-MSI) to interrogate tablet formulations for the spatial distributions of ingredients. Tablet formulations with varying amounts of crystalline acetaminophen (the active pharmaceutical ingredient, API) were analyzed to determine if crystallinity could be evaluated via ELDI-MSI. ELDI-MSI concurrently imaged the API, binders, and surfactants. The spatial distributions of amorphous API were very similar to that of the surfactants and different from that of crystalline API. The higher the crystallinity in the tablet formulation, the more agglomeration of the active ingredient was observed by ELDI-MSI. This study shows the capability of ELDI-MSI to diagnose agglomeration and crystallinity content in pharmaceutical preparations with little to no sample preparation. The ability to concurrently image APIs with other components provides valuable information as to their form in the tablet.
关键词： ELDI,crystallinity,mass spectrometry imaging,pharmaceuticals,agglomeration
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Revealing phase separation and crystallinity in small molecule solar cells using 3D electron microscopy
摘要： Transmission Electron Microscopy (TEM) can be utilized to understand the morphology of organic bulk heterojunction (BHJ) solar cells and thus aid in improving device performance. We have previously shown that phase separation and formation of crystallinity is to be expected during co-evaporation of small molecule BHJ layers [1]. Using Electron Spectroscopic Imaging (ESI) [2] and electron diffraction, we found a significant influence of substrate and substrate temperature on the morphology of the photoactive layer during the fabrication of F4ZnPc:C60 BHJs. Whether or not the device is fabricated as inverted [3] or non-inverted cell influences crystal growth and, thus, phase separation during film formation. We have found that heating the substrate during BHJ film formation leads to an increase in efficiency for the inverted cell, whereas the non-inverted device shows no improvement. While the ESI measurements showed that substrate heating facilitates phase separation of the two materials, the difference in efficiency of the different device architectures could not be explained by this. Electron diffraction data indicated that crystallinity plays a role here. Since conventional ESI and electron diffraction only provide information about material distribution and crystallinity in a two-dimensional projection of the BHJ layers, high-resolution electron tomography was performed to gain insight into the three-dimensional structure. F4ZnPc:C60 was co-evaporated onto layers of neat F4ZnPc and C60, respectively. The measurements were performed under low-dose and LN2-cryo conditions in an FEI Titan Krios. This was necessary to preserve the sample, and foremost its crystallinity, since carbon-based materials, like C60, are prone to severe damage by electron irradiation. Figure 1 shows a bright-field TEM image of the BHJ on C60 (gold fiducials, seen in black, were used for tilt-series alignment). All images of the acquired tilt-series show crystalline areas such as the ones marked (A,B,C). The crystalline spacing seen here can be identified in the power spectra as characteristic for C60 (red: 0.85 nm, green: 0.5 nm and blue: 0.44 nm). As illustrated, such crystallinity can also be visualized in high-resolution electron tomograms, albeit only for smaller volumes at quite high magnification. To obtain a statistically significant distribution of crystallinity for different cell architecture and cell fabrication, larger volumes need to be analysed. For a given detector size, one needs to apply lower magnifications which results in lower resolution. However, the signature of pure crystals at these imaging conditions are a low variance in 3D, i.e. crystal distributions can easily be obtained from segmented 3D variance maps. A slice through the tomographic reconstruction of such samples can be seen in figure 2. Here, a BHJ film on C60 substrate is compared with a similar section through a tomogram of the BHJ on F4ZnPc. The gold fiducial indicates the top of the BHJ film. The homogeneous, aka crystalline areas are highlighted (red overlay). From the distribution of crystallinity we deduce, that large C60 crystals are found in both device architectures causing a very rough film surface. In the inverted device, these crystals can extend throughout the whole film, using the polycrystalline C60 substrate as seed for crystal growth, whereas the non-inverted BHJ showed C60 crystals starting somewhere in the middle of the film. Correlating this data with device performance, we find that C60 crystals which have grown throughout the BHJ layer are crucial for efficient devices.
关键词： Solar Cells,Crystallinity,Tomography,Organic Photovoltaic,CryoTEM
更新于2025-09-11 14:15:04
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Solution-Processable All-Small-Molecule for High-Performance Nonfullerene Organic Solar Cells with High Crystallinity Acceptor
摘要： In this work, two small molecule acceptors (IDIC and IDIC-4F) with different crystallinity and energy level have been successfully applied in nonfullerene-based all-small molecule organic solar cells (NFASM-OSCs). The donor of DFDT(DPP)2 was chosen because of complementary absorption with IDIC and IDIC-4F. As acceptor, IDIC-4F exhibited a higher PCE than IDIC due to better crystallinity. This work not only shows us how to balance the relationship between Voc and Jsc, but also suggests us how to get a good phase separation morphology. Moreover, Increased crystallinity helps to inhibit bimolecular recombination and increase charge mobility. By optimizing device preparation conditions, the best PCE of 9.43% for DFDT(DPP)2 : IDIC-4F as active layer was achieved with excitable Jsc (16.83 mA cm-2) and FF (0.65). The FF and Jsc of resultant device show a significant increased which is among the top efficiencies based on DPP as terminal acceptor groups of NFSM-OSCs reported in document up to now.
关键词： crystallinity,small molecule acceptors,phase separation morphology,nonfullerene organic solar cells,charge mobility
更新于2025-09-11 14:15:04
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Energetic Disorder and Activation Energy in Efficient Ternary Organic Solar Cells with Nonfullerene Acceptor Eh‐IDTBR as the Third Component
摘要： Solution processed ternary organic solar cells (OSCs) contain a third component in the active layer besides the donor/acceptor materials. Two main avenues are considered to fabricate ternary OSCs: (i) to improve the short circuit current density by the selected third component that can broaden and/or enhance the absorption of the host films; (ii) to increase the fill factor by adding materials with diverse crystallinity to tune the film morphology. However, little work has been reported for the improvement of open circuit voltage (VOC), energetic disorder, charge transfer state energy (ECT), and activation energy in ternary OSCs. Herein, we used ternary OSCs with active layer composed of PCE10: F8IC: Eh-IDTBR as model to examine these parameters besides the morphology. We found in the ternary device that the additional Eh-IDTBR improved the crystallinity of the acceptor phase in the ternary mixture; the VOC was 58 mV higher than that of the reference caused by the reduced energetic disorder; due to the good miscibility of Eh-IDTBR with both PCE10 and F8IC, only 50 meV in ECT was observed; zero field activation energy was lower than that for the reference. Our findings provide an alternative way to understand the complex ternary structural-electrical properties correlations.
关键词： ternary organic solar cells,charge transfer state energy,crystallinity phase,energetic disorder,activation energy
更新于2025-09-11 14:15:04
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Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells
摘要： Polymer aggregation and crystallization behavior play a crucial role in the performance of all-polymer solar cells (all-PSCs). Gaining control over polymer self-assembly via molecular design to influence bulk-heterojunction active-layer morphology, however, remains challenging. Herein, we show a simple yet effective way to modulate the self-aggregation of the commonly used naphthalene diimide (NDI)-based acceptor polymer (N2200), by systematically replacing a certain amount of alkyl side-chains with compact bulky side-chains (CBS). Specifically, we have synthesized a series of random co-polymer (PNDI-CBSx) with different molar fractions (x = 0–1) of the CBS units and have found that both solution-phase aggregation and solid-state crystallinity of these acceptor polymers are progressively suppressed with increasing x as evidenced by UV-Vis absorption, photoluminescence (PL) spectroscopies, thermal analysis and grazing incidence X-ray scattering (GIWAXS) techniques. Importantly, compared to the highly self-aggregating N2200, photovoltaic results show that blending of more amorphous acceptor polymers with donor polymer (PBDB-T) can enable all-PSCs with significantly increased PCE (up to 8.5%). The higher short-circuit current density (Jsc) results from the smaller polymer phase-separation domain sizes as evidenced by PL quenching and resonant soft X-ray scattering (R-SoXS) analyses. Additionally, we show that the lower crystallinity of the active layer is less sensitive to the film deposition methods. Thus, the transition from spin-coating to solution coating can be easily achieved with no performance losses. On the other hand, decreasing aggregation and crystallinity of the acceptor polymer too much, reduces the photovoltaic performance as the donor phase-separation domain sizes increases. The highly amorphous acceptor polymers appear to induce formation of larger donor polymer crystallites. These results highlight the importance of a balanced aggregation strength between the donor and acceptor polymers to achieve high-performance all-PSCs with optimal active layer film-morphology.
关键词： morphology control,crystallinity,polymer aggregation,naphthalene diimide,all-polymer solar cells
更新于2025-09-11 14:15:04
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Enhancement of molecular-level ordering of isoindigo based organic materials through deprotecting of cleavable carbamate groups with long alkyl chains
摘要： A new highly soluble isoindigo based organic material with both cleavable carbamate protecting groups bearing long alkyl chains and thiophene groups was successfully synthesized. The carbamate protecting groups were easily removed by solvent-vapor thermal annealing using a mixture of trifluoroacetic acid and chloroform. Deprotection of the NH functional groups in the isoindigo backbone in situ facilitated H-bonding that dramatically improved the strength of the intermolecular interactions. X-ray diffraction and high-voltage electron microscopy studies of the resulting organic material showed long-range ordered crystalline structure. High crystallinity due to enhanced π-π stacking and hydrogen bonding significantly improved the charge carrier mobility. The hole mobilities of isoindigo based organic material measured by SCLC method improved from 3.46 x 10^-6 cm^2 V^-1 s^-1 to 1.13 x 10^-3 cm^2 V^-1 s^-1 upon deprotection of the NH functional groups.
关键词： Isoindigo,Conjugated,Crystallinity,Hydrogen bonding,Protecting groups
更新于2025-09-11 14:15:04
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STRUCTURAL AND MECHANICAL CHARACTERIZATION OF DEFORMED POLYMER USING CONFOCAL RAMAN MICROSCOPY AND DSC
摘要： Polymers have various interesting properties, which depend largely on their inner structure. One way to in?uence the macroscopic behaviour is the deformation of the polymer chains, which e?ects the change in microstructure. For analyzing the microstructure of non-deformed and deformed polymer materials, Raman spectroscopy as well as di?erential scanning calorimetry (DSC) were used. In the present study we compare the results for crystallinity measurements of deformed polymers using both methods in order to characterize the di?erences in micro-structure due to deformation. The study is ongoing, and we present the results of the ?rst tests.
关键词： Raman spectroscopy,DSC,crystallinity,deformed polymers
更新于2025-09-10 09:29:36
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Optical characterization of SiC films grown on Si(111)
摘要： Thin SiC films, grown on Si by substitution of C into Si on Si substrates with and without a SiGe buffer layer, have been investigated with optical techniques. The formation of SiC domains leads to strong green and blue photoluminescence from stacking faults and surface oxides. Introduction of a 10-nm-thick SiGe buffer layer leads to improved crystallinity as evidenced by X-ray diffraction and optical second-harmonic generation (SHG). Nonlinear optical azimuthal rotational spectra demonstrate the presence of cubic SiC in the film. Furthermore, angle-of-incidence scans are consistent with simulations based on a film with cubic symmetry which demonstrates that the cubic phase dominates the SiC film. Growth on vicinal Si(111) leads to a SiC film with the same c1v symmetry as the substrate, demonstrating that the lattice planes of the SiC film follow those of the Si substrate. Spatially resolved SHG scans show structures that are related to the underlying structure of the Si interface resulting from the growth process.
关键词： second-harmonic generation,optical characterization,SiC films,photoluminescence,crystallinity
更新于2025-09-10 09:29:36