•We realized polymorphs of VOPc films on polymer-modified substrates.•Phase II of VOPc films were obtained on PMMA/SiO2, Phase I on PVA.•Balanced ambipolar transport was observed for the VOPc films on PMMA.•Only electron transport was observed on PVA.•Different transport behaviors could be original from their crystalline structures.Polymorphs of vanadyl-phthalocyanine (VOPc) films were realized on the polymer-modified substrates. Balanced ambipolar transport was observed in the Phase II of VOPc film on the PMMA modified substrate, while only electron transport was obtained on PVA layer. The different transport behavior is believed to be original from their crystalline structures, which may lead to their different energy-band structures.Graphical abstract

Polyoctylfluorene thin films were made using novel solvent vapor assisted spin-coating method, which adds solvent into spin-coater and seal it for several minutes before spin-coating to form a solvent vapor atmosphere. The absorption, photoluminescence spectra, electroluminescence spectra and X-ray diffraction patterns demonstrate that β phase directly generate in such thin film while the thin film made by using normal method is amorphous, which means such method combines normal spin-coating and solvent vapor annealing together into one simply and fast process. The brightness and efficiency of related electroluminescence device are also enhanced due to the self-dopant effect.Graphical abstractHighlights► Solvent vapor assisted spin-coating (SVASP) method is proposed. ► SVASP is equivalent to combination of spin-coating and solvent vapor annealing. ► β Phase PFO can directly generate using SVASP method.

•Solvent vapor assisted spin-coating (SVASP) method is proposed.•SVASP is equivalent to combination of spin-coating and solvent vapor annealing.•Higher crystallinity and mobility can be directly achieved.The P3HT thin films were made by novel solvent vapor assisted spin-coating method that adds several opened bottles of solvent into spin-coater and seals it with a lid. Such thin films directly had broader absorption and higher crystallinity. The corresponding thin film transistor had higher mobility of 0.041 cm2 V−1 s−1contrasting to 0.007 cm2 V−1 s−1of device based on P3HT thin film made by normal spin-coating. Compared with the solvent vapor annealed P3HT thin film made by normal spin-coating, the thin film made by solvent vapor assisted spin-coating has similar absorption spectrum, X-ray diffraction and device performance, which demonstrates that such novel method is equivalent to the combination of normal spin-coating and solvent vapor annealing. However the fabrication is more simple and the process time is reduced from several hours to several tens of seconds, which is more beneficial for actual mass production.

PFO thin films made of toluene solution dissolved for 12, 30 and 80 min at 55 °C were prepared and then treated by solvent vapor annealing or thermal annealing. Their absorption, photoluminescence, electroluminescence and morphology were characterized. The results show that the thin film made of solution dissolved for short time contains trace β phase PFO that lead to unusual emission. After solvent vapor annealing or thermal annealing, luminescence of such thin film is lower than that made of solution dissolved for long time. The surface morphology shows that such thin film contains large aggregations with size of 120 × 80 nm, which is in line with the light scattering results of 120 nm large particles in the solution, indicating the difference of luminescence originate from the residue aggregations. Such aggregations will lead to stronger diffraction peak in the in-plane GIXRD and weaker diffraction peak in the out-of-plane GIXRD, which indicates they have more ordered structure in main chain direction that will hinder the formation of ordered packing of PFO molecular chains in out-of-plane direction. These results demonstrate that the PFO solution needs to be dissolved for enough time to realize repeatment of high quality light-emitting device for actual massive application.Graphical abstractHighlights► Short dissolving time will lead to residue aggregations in PFO solution. ► Residue aggregations will be kept in corresponding thin film. ► Residue aggregations will lead to unusual emission and reduce luminescence. ► The poor performance originates from more defects in residue aggregations. ► Solution preparation condition is a key factor for repeatability of PLED.

As spin-coating polyoctylfluorene (PFO) thin films were thermally annealed at various temperatures and their photoluminescence, electroluminescence and crystalline nanostructure was characterized. α phase PFO generate when annealing temperature reaches 80 °C and the performance of corresponding electroluminescence device was dramatically enhanced due to the self-doping effect. As the annealing temperature increases, the photoluminescence and electroluminescence decrease. Both in out-of-plane and in-plane grazing incident X-ray diffraction pattern the PFO thin film annealed at higher temperature has stronger diffraction peaks, indicating higher degree of crystallinity. The formation of vacancy defects and increase of interface roughness in crystalline process is considered as the reason for the reduction of luminescence. These results show that the electro-optical properties of PFO can be enhanced through controlling annealing temperature to form α phase PFO in low degree of crystallinity.Graphical abstract

β phase polyoctylfluorene thin films were obtained by exposure to toluene vapor for various annealing times or dipping into a THF/methanol mixture. The photoluminescence and electroluminescence of PFO thin films decrease with increasing annealing time. Grazing incident X-ray diffraction of the thin films indicates that more and larger β phase crystallites will be generated in thin film exposed for longer time, which will lead to more defects that reduce photoluminescence and electroluminescence. By analyzing the mechanism of formation of β phase, we assume that the defects mainly come from the formation of out-of-plane crystalline structure. The assumption is confirmed by higher photoluminescence of β phase polyoctylfluorene thin film achieved by dipping into a THF/methanol mixture that has less out-of-plane crystalline structure.Highlights► Longer solvent annealing time will lead to more and larger β phase PFO crystallites. ► PL and EL decrease with increasing solvent annealing time. ► Decrease of PL and EL is caused by vacancy defects generated in the crystallization process.► Dipping method will lead to less out-of-plane ordered structure and higher PL. ► Vacancy defects mainly come from the formation of out-of-plane crystalline structure.

A facile and efficient approach has been developed to speed up the fabrication of LBL films through sequential dipping in vigorously agitated solutions. By this agitated-dipping (AD) LBL technique, the multilayer films of PAH and PSS were fabricated. The resulting films were explored by UV−vis spectroscopy, X-ray reflectivity, and AFM. Meanwhile, the comparison of the AD and conventional LBL films was made, which demonstrated that AD LBL can decrease dipping time by more than 15 times without reducing film quality remarkably. In addition, to verify the generality of AD LBL, we studied the AD LBL films of PDDA/PSS and PAH/PAA preliminarily as well. AD LBL promotes the efficiency of conventional LBL greatly while preserving its most advantages, such as simplicity, cheapness, precise control, universality in substrates, recycling use of sample solutions, and so on. It would be a promising alternative to build up LBL films rapidly.

β phase polyoctylfluorene thin films were obtained by exposure to toluene vapor for various annealing times or dipping into a THF/methanol mixture. The photoluminescence and electroluminescence of PFO thin films decrease with increasing annealing time. Grazing incident X-ray diffraction of the thin films indicates that more and larger β phase crystallites will be generated in thin film exposed for longer time, which will lead to more defects that reduce photoluminescence and electroluminescence. By analyzing the mechanism of formation of β phase, we assume that the defects mainly come from the formation of out-of-plane crystalline structure. The assumption is confirmed by higher photoluminescence of β phase polyoctylfluorene thin film achieved by dipping into a THF/methanol mixture that has less out-of-plane crystalline structure.Highlights► Longer solvent annealing time will lead to more and larger β phase PFO crystallites. ► PL and EL decrease with increasing solvent annealing time. ► Decrease of PL and EL is caused by vacancy defects generated in the crystallization process.► Dipping method will lead to less out-of-plane ordered structure and higher PL. ► Vacancy defects mainly come from the formation of out-of-plane crystalline structure.