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Chemical vapor deposition method can prepare perovskite films with controllable morphology and adjustable photoelectric properties. In this work, we have prepared CsPbI2Br films at 400 °C–700 °C using chemical vapor deposition method. The grain size of perovskite film increases with the deposition temperature increment because higher temperature provides greater driving force for nucleation expansion. CsPbI2Br film deposited at 600 °C shows nanofiber structure with polycrystalline property accompanied by local single crystal structure. Steady-state and time-resolved fluorescence measurement explored the charge carrier recombination process of perovskite films. The photodetector based on CsPbI2Br film deposited at 600 °C shows excellent photoelectric response and switching ratio characteristics. This is ascribed to low defect density and fast charge transport along 1D fiber channels. [ABSTRACT FROM AUTHOR]

Suitable solvent additives provide an effective means to control the morphology of polymer blend films. In this work, we systematically investigate the impact of the solvent additive chloronaphthalene (CN) on the morphology of P3HT : EP-PDI blends. The optimum volume fraction of solvent additive CN was found to be 0.5 vol% by atom force microscopy and transmission electron microscopy. UV–visible absorption spectroscopy and grazing incidence x-ray diffraction indicate that the crystallinity of both the P3HT and EP-PDI domains significantly decreased in the blends with 0.5 vol% CN. Grazing incidence small-angle x-ray scattering results show that the size of the small EP-PDI aggregation decreases from 44–22 nm with the addition of CN. Time-resolved photoluminescence measurement reveals that the decreased EP-PDI domains give rise to increased donor–acceptor interfacial areas, which not only facilitate the exciton dissociation, but suppresses the formation of the EP-PDI intermolecular state. [ABSTRACT FROM AUTHOR]

The effect of alkyl side-chain length on the photophysical, morphology and photoresponse properties of poly (3-alkylthiophene) (P3AT) has been investigated. Butyl, hexyl, octyl, decyl, and dodecyl side chains have been studied. In solution state, the average lifetime of poly (3-octylthiophene) (P3OT) is the shortest among P3AT solution owing to the strong intrachain interaction. The fluorescence lifetime of P3AT solution increases with the side-chain length increasing. A similar trend occurs in the P3AT films. This phenomenon illustrates conformation ‘memory’ property evolving from solution state to solid film. The four lifetimes represent different photophysical processes and have been systematically analyzed. The photodetector based on P3DDT is a suitable candidate for practical application owing to the fast, reversible photoresponse and photostability. The high performance of P3DDT-based photodetector is correlated to the optimized morphology and strong interchain interaction which promotes the exciton delocalization. [ABSTRACT FROM AUTHOR]

The introduction of small amounts of carboxylic multi-walled carbon nanotubes into regio-regular poly(3-hexylthiophene) (P3HT) can vary the structure and optical properties of the polymer. The microstructure of the composite film was analysed by various techniques including x-ray diffraction, ultraviolet–visible optical absorption, Raman spectroscopy, and Fourier-transform infrared spectroscopy. It is shown that the presence of carbon nanotubes can improve the crystallinity and increase the conjugation length of P3HT in the films. Furthermore, an obvious photoluminescence quenching is observed in the P3HT/CNTs composite films, suggesting the possibility of photoinduced electron transfer between P3HT and carbon nanotubes due to the π–π interaction of these two components. These results are important for applications in bulk heterojunction solar cells and organic photo-detectors. [ABSTRACT FROM AUTHOR]