Structures of spin-coated and annealed monolayer and multilayer poly(3-dodecylthiophene) thin films

Abstract

The effects of film thickness and post annealing on the edge-on ordering and grain-size of spin-coated P3DDT films, which are of immense importance for their better device performances, were investigated using complementary XR and AFM techniques.

Improved Exciton Bandwidth and Edge-On Oriented Ordering of Donor–Acceptor Copolymer Thin Films

“…The models with gradual evolution, relevant for the XR data analysis, are shown schematically in Figure to understand the analysis and to correlate the parameters with the film structures. For the analysis, each film of thickness, D , was divided into a number of lamellar, after incorporating an interfacial oxide layer above the substrate. , Each lamellar represents a bilayer of thickness d consists of a high electron density (ρ bb ) fused-aromatic backbone layer of donor and acceptor moieties of thickness d bb and a low electron density (ρ sc ) alkyl-side chain layer of thickness d sc (as shown schematically in Figure ). The uniform electron density contrast between the backbone and alkyl-side chain layers (i.e., Δρ = ρ bb – ρ sc ) along the z -direction of the film was unable to fit the XR data properly at the time of data analysis.…”

“…To quantify this, the power spectral density (PSD) profiles for the two films, obtained from the AFM images, are shown in Figure . It can be noted that the PSD is the angular averaged radial distribution of the Fourier transformed height fluctuation data (AFM image). , The wave vector ( k ), where a major change in the slope of PSD profile takes place, corresponds to a certain in-plane correlation length in the system. The correlation length (ξ) that is obtained here from the k -value indicated by the dashed line in the PSD profile (Figure ) can be correlated with the in-plane width of the fibers.…”

Vibronic States and Edge-On Oriented π-Stacking in Poly(3-alkylthiophene) Thin Films

“…The simulation based on such model, though not up to the mark (shown in the left-hand side of Figures S3–S5 of the Supporting Information), can provide the average thickness ( D ) and the average electron density (ρ a ) of the film as shown in Table . Next each film of thickness D was divided into a number of bilayers after an interfacial oxide layer was incorporated above the substrate. ,, Each bilayer of thickness d consists of a high electron density (ρ bb ) polythiophene backbone layer of thickness d bb and a low electron density (ρ sc ) alkyl side-chain containing a layer of thickness d sc . A simulation was then performed considering the bilayer ( d = d bb + d sc ) stack of uniform electron density contrast (Δρ = ρ bb – ρ sc ) along the z -direction.…”

“…The major effect of the thermal energy is, however, on the EO ordering of the P3AT. The thermal energy mainly helps in the reorientation of the crystalline aggregates, rather than their growth, to attend the EO ordering (which is probably favorable or an energy-minimum configuration , ). The EO ordering is found to improve gradually throughout the film with the increase of thermal energy (i.e., annealing temperature).…”

Nanoparticle Mediated Improved Crystallinity and Connectivity of Semiconducting Polymer Thin Films

“…The locations of the dispersed conducting NMs in the PNC film are of prime importance in deciding its device performances. For example, the locations of the NMs in the amorphous polymer regions can establish better contacts between crystallites and also can improve the overall crystallinity (in terms of quantity and quality) of the polymer matrix, both of which in turn can enhance the charge carrier mobility of the system. , Such information, which are of utmost importance, can be extracted using complementary X-ray reflectivity (XR) and optical absorption techniques. , XR is capable of providing electron density profile (EDP), i.e., in-plane ( x – y ) average electron density as a function of depth ( z ), − from which information about the aggregation and/or distribution of NMs along depth ,, and the layering due to ordering of polymer can be obtained, − while the optical absorption is capable of providing information about the intra- and interchain ordering, the conjugation length, and the percentage of crystalline polymer aggregates in the system. ,, However, such characterization of PNC thin films containing semiconducting polymers using complementary techniques, in general and XR technique, in particular, through nondestructive ways, are very rare.…”