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Determining the Effect of Different Heat Treatments on the Electrical and Morphological Characteristics of Polymer Solar Cells
摘要： The device characteristics of polymer solar cells can be improved through an annealing process. This is especially true of the carrier mobility and the light absorption of P3HT:PCBM, which improves considerably after the annealing process. In the standard structure using indium-tin-oxide (ITO) as an anode, most studies have focused on the post-annealing process, where thermal annealing is performed after device fabrication. This work reports the effects of different annealing methods for inverted polymer solar cells, using ITO as a cathode. Similar levels of light absorption and P3HT crystallinity were obtained regardless of the annealing procedure in the inverted structure. However, compared with the post-annealed device, the pre-annealed device, which was thermally annealed after deposition of the P3HT:PCBM film, exhibited better charge extraction, owing to the superior device resistances and larger MoO3 grain size. Therefore, the pre-annealing method yields better performance than the post-annealing method.
关键词： Inverted polymer solar cell,Heat treatment,Morphology,Impedance
更新于2025-09-16 10:30:52
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Surface morphology evolution during pulsed selective laser melting: Numerical and experimental investigations
摘要： A novel physical model for the selective laser melting (SLM) was proposed, providing insights into the surface morphology evolution in the pulsed SLM process. Both Marangoni effect and recoil pressure, which were the prevailing driving forces for the melt flow, were incorporated in the model. It was found that the melt track was characterized by regular fish scale patterns in pulsed remelting process, due to the periodic variation of the molten pool, while the melt track exhibited with a smooth surface under a continuous laser mode. The effect of the exposure time on the surface morphology was also investigated during pulsed SLM process. It was shown that the longer exposure time could produce greater recoil pressure and sufficient molten liquid, leading to a more congested fish scale patterns. The surface defects such as distortions and breakups were strongly associated with the distribution characteristics of the powders. The partially melted particles which attached to the melt flow were the main reasons to the formation of distortions. And the formation the breakups could be attributed to the local lacking of the powders. The simulated results were in good agreement with the experimental results.
关键词： Surface morphology,Surface defects,Pulsed selective laser melting,Exposure time,Molten pool evolution
更新于2025-09-16 10:30:52
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Aloe vera-peel derived porous carbon integrated Co/Mn-oxide based nano-hybrids: An efficient electrocatalyst in advanced photovoltaics
摘要： We propose a facile strategy to synthesize highly electrocatalytic active nanohybrids by the integration of aloe vera-peel derived porous carbon into manganese-based and cobalt/manganese-based oxides. These nanohybrids exhibit unique three-dimensional porous network structures and possess high surface areas, providing numerous catalytic sites and multiple rapid electron transfer channels. In this work, the as-synthesized nanohybrids are used as accelerants for tri-iodide reduction in dye-sensitized solar cells, resulting in attractive cell efficiency and superior electrochemical stability. The solar cell with low-cost bio-based carbon integrated cobalt/manganese-oxide counter electrode exhibits higher photovoltaic efficiency than that of platinum electrode (7.01% vs. 6.44%). In addition, hybrid catalyst loaded counter electrodes also demonstrate long-term electrochemical stability in I3?/I? electrolyte, retaining 97% of its initial efficiency (6.83%/7.01%) in working cell, after going through multiple cyclic voltammetry scans. The utilization of synergistic effects of high performance constituents and controlled morphology is a key strategy to intensify the catalytic activity, electrochemical stability, and power conversion efficiency in advanced photovoltaics.
关键词： Dye-sensitized solar cell,Bio-based porous carbon,Cobalt manganese oxide,Morphology transformation,Electrocatalytic accelerants
更新于2025-09-16 10:30:52
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Atomistic kinetic Monte Carloa??Embedded atom method simulation on growth and morphology of Cua??Zna??Sn precursor of Cu <sub/>2</sub> ZnSnS <sub/>4</sub> solar cells
摘要： An atomistic kinetic Monte Carlo coupled with the embedded-atom method is used to simulate film growth and morphology evolution of a Cu–Zn–Sn precursor of Cu2ZnSnS4 solar cells by single-step electrodeposition. The deposition and diffusion events of three different metallic atoms are described by the simulation. Moreover, the multibody Cu–Zn–Sn potential is used to calculate diffusion barrier energy. The effects of process factors, including temperature and electrode potential, on the cross-section morphology and surface roughness are explored, while keeping the elemental composition ratios constant. The lowest roughness with the smoothest morphology is obtained at the optimal parameters. The distribution and transformation behaviors of cluster sizes are investigated to describe the alloy film growth process. Furthermore, the comparison between deposition events and diffusion events reveals that deposition events depend primarily on individual deposition rates of different metallic atoms, but diffusion events are mainly dependent on the interaction of metallic atoms. The film morphology evolution is visualized by three-dimensional configuration with increasing numbers of atoms, which suggests a competing mechanism between nucleation and growth of the thin film alloy.
关键词： Cu–Zn–Sn precursor,film growth,Cu2ZnSnS4 solar cells,electrodeposition,atomistic kinetic Monte Carlo,morphology evolution,embedded-atom method
更新于2025-09-16 10:30:52
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Critical Role of Polymer Aggregation and Miscibility in Nonfullerenea??Based Organic Photovoltaics
摘要： Understanding the correlation between polymer aggregation, miscibility, and device performance is important to establish a set of chemistry design rules for donor polymers with nonfullerene acceptors (NFAs). Employing a donor polymer with strong temperature-dependent aggregation, namely PffBT4T-2OD [poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3″′-di(2-octyldodecyl)-2,2′;5′,2″;5″,2″′-quaterthiophen-5,5-diyl)], also known as PCE-11 as a base polymer, five copolymer derivatives having a different thiophene linker composition are blended with the common NFA O-IDTBR to investigate their photovoltaic performance. While the donor polymers have similar optoelectronic properties, it is found that the device power conversion efficiency changes drastically from 1.8% to 8.7% as a function of thiophene content in the donor polymer. Results of structural characterization show that polymer aggregation and miscibility with O-IDTBR are a strong function of the chemical composition, leading to different donor–acceptor blend morphology. Polymers having a strong tendency to aggregate are found to undergo fast aggregation prior to liquid–liquid phase separation and have a higher miscibility with NFA. These properties result in smaller mixed donor–acceptor domains, stronger PL quenching, and more efficient exciton dissociation in the resulting cells. This work indicates the importance of both polymer aggregation and donor–acceptor interaction on the formation of bulk heterojunctions in polymer:NFA blends.
关键词： nonfullerene acceptors,charge transport,morphology,charge generation,polymer aggregation
更新于2025-09-16 10:30:52
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Influence of Polymer Aggregation and Liquid Immiscibility on Morphology Tuning by Varying Composition in PffBT4Ta??2DT/Nonfullerene Organic Solar Cells
摘要： The temperature-dependent aggregation behavior of PffBT4T polymers used in organic solar cells plays a critical role in the formation of a favorable morphology in fullerene-based devices. However, there is little investigation into the impact of donor/acceptor ratio on morphology tuning, especially for nonfullerene acceptors (NFAs). Herein, the influence of composition on morphology is reported for blends of PffBT4T-2DT with two NFAs, O-IDTBR and O-IDFBR. The monotectic phase behavior inferred from differential scanning calorimetry provides qualitative insight into the interplay between solid–liquid and liquid–liquid demixing. Transient absorption spectroscopy suggests that geminate recombination dominates charge decay and that the decay rate is insensitive to composition, corroborated by negligible changes in open-circuit voltage. Exciton lifetimes are also insensitive to composition, which is attributed to the signal being dominated by acceptor excitons which are formed and decay in domains of similar size and purity irrespective of composition. A hierarchical morphology is observed, where the composition dependence of size scales and scattering intensity from resonant soft X-ray scattering (R-SoXS) is dominated by variations in volume fractions of polymer/polymer-rich domains. Results suggest an optimal morphology where polymer crystallite size and connectivity are balanced, ensuring a high probability of hole extraction via such domains.
关键词： PffBT4T-2DT,nonfullerene organic solar cells,liquid immiscibility,O-IDTBR,polymer aggregation,O-IDFBR,morphology tuning
更新于2025-09-16 10:30:52
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Achieving Efficient and Stable Morphology in Organic Solar Cells via Fine-tuning the Side-chains of Small Molecule Acceptors
摘要： Both the efficiency and stability of low cost organic solar cells are central components to meeting the requirements of commercialization for organic photovoltaics (OPV). Furthermore, the relationship between chemical structure of active material and morphology and its effects on efficiency and stability is still largely undetermined. Additionally, both the kinetic and thermodynamic morphology states of active layer can have a large impact on efficiency and stability, even when the chemical structures of materials applied in the active layer are especially same or similar. Here, using two series of acceptor-donor-acceptor (A-D-A) type small molecule acceptors (SMAs) with the similar backbone structure, we demonstrate the relevance of fine-tuned chemical structures with their solution and solid-state properties, further leading to significantly different behavior in terms of both device efficiency and stability. This is also partially due to the different morphology states caused by such fine chemical structure tuning. Our results indicate that a delicate balance of molecular aggregation and ordered stacking morphology is not only required to achieve but also could lead to both high efficiency and stability. Thus, among the two series of molecules, UF-EH-2F with both optimal length and steric hindrance of side-chains achieves the preponderant morphology in its corresponding device, where its morphology “Efficient State” and “Stable State” are almost overlapped and thus lead to both the highest efficiency (PCE = 13.56%) and best stability. Our results indicate that it is highly possible to achieve the morphology state required for both high efficiency and stability simultaneously by fine-tuning the chemical structure of active materials for organic solar cells.
关键词： small molecule acceptors,efficiency,side-chains,morphology,organic solar cells,stability
更新于2025-09-16 10:30:52
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Size Effect of Two Dimension Conjugated Space in Photovoltaic Polymersa?? Side-chain: Balancing Phase Separation and Charge Transport
摘要： Various two-dimension (2D) side-chains substituted benzo(1,2-b:4,5-b’)dithiophene (BDT) blocks have been used to construct donor polymers, while the size effect of side-chains on photovoltaic performance was overlooked in past few years. This work, three size varied conjugated space (benzene, naphthalene and biphenyl) were introduced into corresponding polymers PBDB-Ph, PBDB-Na and PBDB-BPh. This space engineering has significant impact on the extent of phase separation in active layer which blended with polymer and acceptor ITCPTC and preserved the desired morphology. Varied space size in side-chains lead to distinct balance mobility ratios of hole to electron (benzene is 0.21, and for naphthalene is 0.75, biphenyl is 0.57). Finally, PBDB-Na-based polymer solar cells (PSCs) delivered the highest power conversion efficiency (PCE) 12.52% when compared to the PSCs performance of PBDB-Ph (8.48%) and PBDB-BPh (11.35%). The mothed in tailoring the side-chains structures could fabricate a balance between phase separation and charge transport, providing an enlightenment for the development of photovoltaic device.
关键词： side-chain,phase separation,desired morphology,charge transport,photovoltaic performance
更新于2025-09-16 10:30:52
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Picosecond laser ablation and depth profile of Cu(In, Ga)Se2 thin film layer
摘要： Laser ablation based on picosecond laser was used to achieve the micro-analysis of Cu(In, Ga)Se2 (CIGS) thin film with the ablation crater diameter of 50 μm and the ablation crater central depth of 93 ± 13 nm. We achieved the depth profile of CIGS thin film with different laser shot number. The evolutions of spectral lines intensities of Ca from glass substrate and Ga and In from CIGS thin film layer, and intensity ratios of Ca/Ga and Ca/In could exhibit the change of the ablation volume, which could estimate the thin film thickness of single CIGS thin film layer. The average plasma temperature was calculated to be about 5243 ± 100 K, and the average electron density was calculated to be about 4.5×1016 cm?3. It is shown that our experimental setup is suitable to achieve a precise control and monitor the element compositions in each CIGS thin film layer in the research and in the production of CIGS solar cells.
关键词： Ablation morphology,Electron density,Cu(In, Ga)Se2 thin film,Picosecond laser induced breakdown spectroscopy,Plasma temperature
更新于2025-09-16 10:30:52
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Synergistic effect of processing solvent and additive for the production of efficient all-polymer solar cells
摘要： Ideal morphological features are of particular importance to produce high performance all-polymer solar cells (all-PSCs), in which the active blends generally involve unfavorable phase separation due to the complicated intermixing. Developing suitable processing solvent and additive is an effective and versatile approach to manipulate the blends morphology. This study demonstrates the synergistic effect of processing solvent and additive to the photovoltaic performances of all-PSCs composed of a conjugated copolymer J71 donor and typical N2200 acceptor. The low boiling point chloroform (CF) solvent combined with 1% 1,8-diiodoctane (DIO) additive was identified as the optimal processing condition to treat the J71:N2200 blends. Consequently, the all-PSCs casting from CF + 1% DIO achieved an outstanding efficiency of 9.34% with an ultrahigh fill factor of 77.86%, which is among the top values for current all-PSCs systems. Owing to the low JSC, just a moderate efficiency of 7.28% was obtained for the device from chlorobenzene (CB) + 1% DIO processing despite of its high FF. The electron microscopic tests revealed that the CF was superior to CB solvent to obtain uniform morphologies and the addition of DIO additive could further generate more favorable phase separation and domain size. Moreover, the results of charge generation, transport, and recombination analysis correlate well with the remarkable photovoltaic properties. Our results highlight the critical significance of selecting appropriate processing solvent and additive to pursue high performing all-PSCs.
关键词： all-polymer solar cells,processing solvent,morphology,additive,photovoltaic performance
更新于2025-09-16 10:30:52