Effects of Material Morphology on the Performance of Organic Electronics

Polymorphic Phase-Dependent Optical and Electrical Properties of a Diketopyrrolopyrrole-Based Small Molecule

“…Such a slight increment in the lattice spacing may be caused by the substrate because it was noticed that the same reflection shifts to 5.56° with increasing thickness of the films (Figure S5). Although the 2D GIXD pattern of the as-spin-coated film depicts the texturing of crystallites along the out-of-plane direction, the amorphous halo confirms the existence of quite a considerable amount of amorphous DPP-(CF) 2 within it. , So, postgrowth thermal annealing was employed to increase the crystallinity of the films.…”

“…In particular, the presence of a broad amorphous halo centered at ≈24° in the 2D GIXD patterns of the films annealed at 82 and 116 °C confirms the existence of quite a considerable amount of amorphous DPP-(CF) 2 within it (Figure S6) even after subtraction of the background scattering (recorded using a PEDOT:PSS-coated glass substrate). Because amorphous DPP-(CF) 2 is detrimental for charge transport, SVA was employed to prepare highly crystalline and highly textured thin films of the DPP-(CF) 2 -α and DPP-(CF) 2 -β phases so as to understand the role of polymorphism on the electronic performance of DPP-(CF) 2 . ,, Because the DPP-(CF) 2 -γ phase obtained by annealing of the film at 166 °C was highly crystalline, the same methodology was employed to obtain a pure form of DPP-(CF) 2 -γ for device analysis.…”

“…SVA was performed using HPLC-grade solvents in a 75 mL closed jar. Thin films were positioned ≈2 mm above the solvent level with the help of clean glass slides . Methanol vapor annealing was performed with an airtight lid, and CHCl 3 vapor annealing was performed by just covering the jar with a Petri dish.…”

“…The polymorphic alteration of OSs can hinder the reliability, reproducibility, and stability of the devices. The postgrowth thermal annealing and SVA methods are commonly applied to the newly synthesized molecules for the realization of efficient organic electronic devices, − which can greatly alter the molecular packing. However, an understanding of the role of polymorphism on the performances of organic electronics is relatively scarce, and most of such studies were conducted using the above-mentioned representative OSs. ,− ,, Followed by those representative OSs, various narrow-band-gap small molecules and polymers have been synthesized by the grafting of various electron-rich moieties such as thiophene, phenyl, bithiophene, thienothiophene, furan, naphthalene, selenophene, etc., onto electron-deficient moieties such as dioxo-3,6-diarylpyrrolo­[3,4- c ]­pyrroles (DPPs), − isoindigo, benzothiadiazole, etc.…”

Post-Growth Dynamics and Growth Modeling of Organic Semiconductor Thin Films

“…Organic electronics typically relies on thin films used as active layers in devices, , whose performances are found to be highly dependent on the film structure and morphology, directly dictating the optoelectronic properties. , For a successful integration in devices, control over the film growth is, therefore, crucial . One of the best techniques to obtain thin films with high control on structure and morphology is organic molecular beam epitaxy (OMBE), which allows fine-tuning of the growth parameters. − Nonetheless, even films grown via OMBE may experience a post-growth evolution in a controlled environment and/or in ambient conditions, through different processes such as wetting, dewetting, or ripening, − often characterized by a change in the morphology and/or structure, − which may affect device performance and long-term stability.…”