Solvent Vapor Annealing Induced Polymorphic Transformation of Polybutene-1

Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials. In this paper, we addressed the effects of solvent vapor annealing, including chloroform and water vapor, on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1 （PB-1） by means of in situ Fourier transform infrared spectroscopy （FTIR）. The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity. Also, a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.

Synergistic Effects of External Electric Field and Solvent Vapor Annealing with Different Polarities to Enhance β-Phase and Carrier Mobility of the Poly(9,9-dioctylfluorene)Films

In this work,the synergistice efects of external electric field(EEF)and solvent vapor annealing to enhanceβ-phase and carrier mobility of poly(9,9-dioctylfuorene)(PFO)films were investigated.It is found that EEF can promote the PFOβ-phase conformation transition and orientate the PFO chains along the EEF direction with the as-sistance of polar solvent vapor annealing.PFO chain orderness is closely related to the solvent polarity.In particular,the B-phase content in the annealed film of strong polar chloroform vapor increases from 18.7%to 34.9%after EEF treatment.Meanwhile a characteristic needle-like crystal is formed in the flm,as a result,the hole mobility is en-hanced by an order of magnitude.The mechanism can be attributed to the fast polarization of solvent dipole under the action of EEF,thus forming a driving force that greatly facilitates the orientation of PFO dipole unit.Research also reveals that EEF driving of the PFO chains does not occur with an insoluble solvent vapor since the solvent molecules cannot swell the film,thus there is insufficient free volume for PFO chains to adjust their conformation.This research enriches the understanding of the relationship between solvent vapor annealing and EEF in orientation polymers,and this method is simple and controlled,and capable of integrating into large-area thin film process,which provides new insights to manufacture low-cost and highly ordered polymer films,and is of great significance to enhance carrier mobility and efficiency of photoelectric devices based on polymer condensed matter physics.

Understanding the synergistic effect of mixed solvent annealing on perovskite film formation

Morphology control of perovskite films is of critical importance for high-performance photovoltaic devices. Although solvent vapor annealing(SVA) treatment has been widely used to improve the film quality efficiently, the detailed mechanism of film growth is still under construction, and there is still no consensus on the selection of solvents and volume for further optimization. Here, a series of solvents(DMF, DMSO, mixed DMF/DMSO) were opted for exploring their impact on fundamental structural and physical properties of perovskite films and the performance of corresponding devices. Mixed solvent SVA treatment resulted in unique benefits that integrated the advantages of each solvent, generating a champion device efficiency of 19.76% with improved humidity and thermal stability. The crystallization mechanism was constructed by conducting grazing-incidence wide-angle x-ray diffraction(GIWAXS) characterizations, showing that dissolution and recrystallization dominated the film formation. A proper choice of solvent and its volume balancing the two processes thus afforded the desired perovskite film. This study reveals the underlying process of film formation, paving the way to producing energy-harvesting materials in a controlled manner towards energy-efficient and stable perovskite-based devices.

Effect of dual annealing upon photovoltaic properties of polymer solar cells based on poly(3-hexylthiophene)

A dual annealing method comprised of toluene vapor treatment and post thermal annealing was employed to fabricate polymer solar cells （PSCs） based on poly（3-hexylthiophene） （P3HT） and [ 6,6 J-phenyl-C61-butyric acid methyl ester （PCBM） film. It is found that the P3HT crystallinity and chain ordering can be dramatically enhanced by this annealing process as compared with the films treated merely with solvent vapor annealing, which is verified by a higher X-ray diffraction intensity peak and clearly visible fibrillar crystalline domains of P3HT. The result suggests that a favorable e- quilibrium condition was established by dual annealing in the morphology reorganization. Due to the morphological improvement of active layer, the dually annealed PSCs show better overall perform- ances, with a mean power conversion efficiency of 4. 06% and an increase in each electrical parame- ter, than any solely annealed ones.

Nanopattern Transformation ofABC Triblock Copolymer Thin Films Induced by Strong Solvent Selectivity and Annealing

Nanopattem transformation behaviors of polyisoprene-block-polystyrene-block-poly（2-vinylpyridine） （PI-b-PS-b-P2VP） asymmetric ABC triblock copolymer were investigated systematically with various control para- meters, including different solvents for polymer solution and annealing conditions in this paper. Ordered nanopattern of PI-b-PS-b-P2VP with hexagonal cylinders could be obtained when PI-b-PS-b-P2VP toluene solution was spin-coated on silicon substrate followed by toluene vapor annealing process. When the film with hexagonal and cylindrical nanopattern was exposed to saturated toluene vapor, the order-order transition of cylindrical nanopattern to parallel nanopattern was observed due to the strong selectivity of toluene to PS and PI blocks. Furthermore, fingerprint nanopattern could also be obtained by solvent annealing in tetrahydrofuran vapor. The nanopattern trans- formation was due to different selectivity of solvents and incompatibilities of the three blocks of PI-b-PS-b-P2VP under various solvent annealing conditions.

18.01%Efficiency organic solar cell and 2.53%light utilization efficiency semitransparent organic solar cell enabled by optimizing PM6:Y6 active layer morphology

Optimizing the photoactive layer morphology is a simple,promising way to improve the power conversion efficiencies(PCEs)of organic solar cells(OSCs).Here,we compared different post-processing treatments on PM6:Y6 blend films and relevant effects on device performances,including as-cast,thermal annealing and solvent annealing.This solvent annealing processes can effectively improve the vertical distribution and aggregation of polymer donors and small molecule acceptors,then optimize the active layer film morphology,ultimately elevating PCE.Thus,one of champion efficiencies of 18.01%was achieved based on the PM6:Y6 binary OSCs.In addition,a relatively high light utilization efficiency(2.53%)was achieved when a transparent electrode made of Cu(1 nm)and Ag(15 nm)was utilized to fabricate a semitransparent OSC with a remarkable PCE of 13.07%and 19.33%average visible-light transmittance.These results demonstrated that carefully optimizing morphology of active layer is conducive to achieving a high-performance OSC.