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Comparative solvent quality dependent crystallization in solvent vapor annealing of P3HT:PCBM thin films by in-situ GIWAXS
摘要： We present a novel in-depth study correlating multiple solvent properties (boiling point, vapor pressure, and solubilities of P3HT and PCBM) on P3HT and PCBM crystal growth kinetics in blend thin films via in-situ GIWAXS in conjunction with multiple substrate energies. Solvent vapor annealed (SVA) P3HT:PCBM films in a closed chamber, saturated with different solvents (o-dichlorobenzene (DCB), o-xylene, tetrahydrothiophene (THT), toluene, benzene, tetrahydrofuran (THF), and carbon disulfide (CS2)) were studied in real time. We observed that structure growth and dissolution kinetics of the both P3HT and PCBM crystals largely depend on physical properties of solvent and relative solubilities of P3HT and PCBM. The film morphology of the annealed films resulted in PCBM enrichment and occasional crystallization occurred at the solvent vapor saturated air interfaces. We observed strikingly different PCBM crystallization upon annealing of the films when cast from THF resulting in highly ordered PCBM crystals at the film surface. THF has high vapor pressure and relatively low solubilities for both P3HT and PCBM. At the other extreme CS2 produced the lowest crystallinity due to its very high vapor pressure such that the solvent evaporates before significant crystallization can occur. We characterized all the annealed samples using AFM, UV-Vis spectroscopy, and XPS. AFM probed topographic structures with coarsening of both the P3HT and PCBM domains at air surface by solvent annealing. We observe via UV-vis spectroscopy that, in general, intrachain electronic delocalization and interchain electron transitional jump due to π-π stacking increases in the post SVA films. This indicates that the chains are better organized with increased conjugation lengths. SVA has a substantial effect on P3HT monomer to PCBM ratio as determined by XPS at the polymer-air interface. In all cases, relative to the P3HT monomer:PCBM ratio of as-cast films from DCB, the air surfaces became more enriched by PCBM with SVA.
关键词： P3HT,GIWAXS,Morphology
更新于2025-09-23 15:23:52
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In situ observation of ?′ phase suppression by lattice strain in all-inorganic perovskite solar cells
摘要： The phase control and ordered crystal growth play a crucial role in the efficiency and stability of all-inorganic perovskite solar cells (PSCs). However, the innate dynamics of crystal growth driving the stable phase and high performance are unknown. Here, we for the first time unraveled that the degree of lattice strain is responsible for the suppression of the δ phase growth by in situ Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS) technique. We shadow the internal crystal structural changes in real time and successfully decoupled crystal growth dynamics under different substrate temperatures. The symmetrical crystal lattice and vertical substrate growth were finally achieved. This finding provides insights on the inorganic perovskite crystal growth and has significant benefit for high performing all-inorganic PSCs.
关键词： GIWAXS,CsPbI2Br,Inorganic halide perovskite,Lattice strain
更新于2025-09-23 15:19:57
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Performance enhancement of conjugated polymer-small molecule-non fullerene ternary organic solar cells by tuning recombination kinetics and molecular ordering
摘要： We present our study of conjugated polymer-small molecule (SM)-non-fullerene ternary organic solar cells (OSCs), which employs conjugated polymer PTB7-Th and small molecule p-DTS(FBTTh2)2 as donors and non-fullerene molecule IEICO-4F as an acceptor. It is observed that the power conversion efficiency (PCE) of ～10.9% for PTB7-Th: p-DTS(FBTTh2)2: IEICO-4F ternary OSCs with 15 wt% of p-DTS(FBTTh2)2 SM is higher than PCE of ～9.8% for PTB7-Th: IEICO-4F OSCs. Morphological studies confirm that the addition of p-DTS(FBTTh2)2 SM in PTB7-Th: IEICO-4F binary blend improves molecular ordering and crystallinity of PTB7-Th due to the favorable interaction with p-DTS(FBTTh2)2 thereby providing 3-D textured structures consisting of a mixture of edge-on and face-on orientations. The improved molecular ordering is shown to enhance exciton generation rate, exciton dissociation, charge collection, and to reduce charge recombination, all of which boosts the PCE.
关键词： PTB7-Th,Ternary,p-DTS(FBTTh2)2,IEICO-4F,GIWAXS,Non-fullerene
更新于2025-09-23 15:19:57
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Barium doping effect on the photovoltaic performance and stability of MA0.4FA0.6BaxPb1-xIyCl3-y perovskite solar cells
摘要： Perovskite solar cells (PSCs) have earned widespread attention owing to its fast-growing power conversion efficiency (PCE). However, there are some challenges for this type of solar cells. The toxicity issue, current density-voltage (J-V) hysteresis, and uncertain stability hinder commercialization. In this study, we developed the PSCs with MA0.4FA0.6BaxPb1-xIyCl3-y film as active layer. The MA0.4FA0.6BaxPb1-xIyCl3-y film with various barium doping concentrations were fabricated by solvent engineering method. We investigate the surface morphology, crystal orientation, and optical property of various perovskite films. Furthermore, the in situ grazing-incidence wide-angle X-ray scattering (in-situ GIWAXS) is used to analyze the heating crystallization process of perovskite film. We discover that Ba can improve crystallinity and structural stability. For the optimal 5.0 mol% Ba replacement, the PCE of perovskite device is increased to 17.4%, the J-V hysteresis can be completely eliminated and the device demonstrates long-term stability.
关键词： in-situ GIWAXS,perovskite solar cell,J-V hysteresis,barium dopant,power conversion efficiency
更新于2025-09-23 15:19:57
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Stress Evolution during Ge Nanoparticles Growth in a SiO <sub/>2</sub> Matrix
摘要： Superstructures are explored that were obtained by multilayer magnetron deposition at room temperature of 20 SiO2 and SiO2:Ge bilayers, each 2 × 4 nm thick, and subsequently annealed in inert N2 atmosphere at different temperatures in the range of 500?750 °C. The structural and optical changes induced by annealing and the formation and growth of Ge nanoparticles (nps) from early clusters to their full growth and final dissolution were studied by the simultaneous grazing-incidence small- and wide-angle X-ray scattering, transmission electron microscopy, and (time-resolved) photoluminescence (PL). It is shown that in as-deposited multilayers aggregation of small clusters already occurred, and the clusters were reasonably well intercorrelated in the lateral plane. During annealing at Ta = 550 °C or higher temperatures, Ge nps start to form and remain partly amorphous at lower Ta but crystallize completely at about 600 °C. At even higher temperatures, the Ge nps dissolve and Ge diffuses out almost completely, leaving voids in the SiO2 matrix. Visible PL from the samples was detected and attributed to defects in the nps/matrix interface layers rather than to the nps itself because PL persisted even after Ge nps dissolution.
关键词： GIWAXS,photoluminescence,Ge nanoparticles,GISAXS,stress evolution,SiO2 matrix,TEM
更新于2025-09-11 14:15:04
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Rapid and sheet-to-sheet slot-die coating manufacture of highly efficient perovskite solar cells processed under ambient air
摘要： A nitrogen-free and slot-die coating fabrication of perovskite solar cells combined with NIR annealing. We develop a fabrication approach of planar inverted structured perovskite solar cell (PSC) in ambient condition with a PCE of 12.4% as compared to that (13.3%) of PSC fabricated in glove box filled with nitrogen. In addition, we demonstrate an alternative post-annealed method by near-infrared (NIR) radiation to traditional heating method by oven. The annealed time by NIR can be shortened from 1500 s to 30 s and the device performance over 10% can be achieved. The present work investigates the NIR effect for different layers in the two-step processing on the cell performance. The grazing-incidence wide-angle and small-angle X-ray scattering (GIWAXS and GISAXS) techniques for the perovskite layers are performed to reveal the crystalline and nano-morphological structures of perovskite layers correlated to thermal and NIR annealing effects. Based on this approach under ambient air, we scale up to the large-area fabrication using the slot-die coating. The performance of slot-die coated PSC can achieve to 12.3%. The critical step is the control of PbI2 layer thickness. We also applied the NIR radiation to the slot-die coated PSC and the PCE of 11.4% can be achieved. Our study paves a facile way to rapid manufacture and mass production of perovskite solar cells.
关键词： Perovskite solar cell,Two-steps,Near-infrared radiation,Slot-die,GIWAXS,GISAXS
更新于2025-09-09 09:28:46
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Designing Conjugated Polymers for Molecular Doping: The Roles of Crystallinity, Swelling, and Conductivity in Sequentially-Doped Selenophene-Based Copolymers
摘要： Although chemical doping is widely used to tune the optical and electrical properties of semiconducting polymers, it is not clear how the degree of doping and the electrical properties of the doped materials vary with the bandgap, valence band level, and crystallinity of the polymer. We address this question utilizing a series of statistical copolymers of poly(3-hexylthiophene) (P3HT) and poly(3-heptylselenophene) (P37S) with controlled gradients in bandgap, valence band position and variable crystallinity. We dope the copolymers in our series with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) using solution sequential processing (SqP). We then examine the structures of the films using grazing incidence wide-angle x-ray scattering (GIWAXS), differential scanning calorimetry (DSC) and ellipsometric porosimetry, and the electrical properties of the films via the AC Hall effect. We find that the ability of a particular copolymer to be doped is largely determined by the offset of the polymer’s valence band energy level relative to the LUMO of F4TCNQ. The ability of the carriers created by doping to be highly mobile and thus contribute to the electrical conductivity, however, is controlled by how well the polymer can incorporate the dopant into its crystalline structure, which is in turn influenced by how well it can be swelled by the solvent used for dopant incorporation. The interplay of these effects varies in a non-monotonic way across our thiophene:selenophene copolymer series. The position and shape of the polaron absorption spectrum correlate well with the polymer crystallinity and carrier mobility, but the polaron absorption amplitude does not reflect the number of mobile carriers, precluding the use of optical spectroscopy to accurately estimate the mobile carrier concentration. Overall, we find that the degree of crystallinity of the doped films is what best correlates with conductivity, suggesting that only carriers in crystalline regions of the film, where the dopant counterions and polarons are forced apart by molecular packing constraints, produce highly mobile carriers. With this understanding, we are able to achieve conductivities in this class of materials exceeding 20 S/cm.
关键词： semiconducting polymers,conductivity,ellipsometric porosimetry,GIWAXS,solution sequential processing,valence band level,F4TCNQ,poly(3-heptylselenophene),AC Hall effect,poly(3-hexylthiophene),DSC,bandgap,chemical doping,crystallinity
更新于2025-09-04 15:30:14