Characterization of spray-coating methods for conjugated polymer blend thin films

Abstract

Noebels, M., Cross, R. E., Evans, D. A., & Finlayson, C. E. (2014). Characterization of spray-coating methods for conjugated polymer blend thin films. Journal of Materials Science, 49(12), 4279-4287We examine the characteristics and functionality of conjugated polymer thin films, based on blends of poly(9,9-dioctylfluorene-2,7-diyl-co-bis-N,NN'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB) and poly(9,9-dioctylfluorene-2,7-diyl-co-benzothiadiazole) (F8BT), using a spray-coating deposition technique suitable for large areas. The morphological properties of these blend films are studied in detail by atomic force microscopy (AFM) methods, showing that favourable results, in terms of layer deposition rate and uniformity, can be achieved using a 5:1 blend of o-dichlorobenzene and chlorobenzene as the solvent medium. A photoluminescence quenching efficiency of above 80 % is also observed in such blend films. As a feasibility study, prototypical photovoltaic devices exhibit open circuit voltages of up to 1.0 V under testing, and solar power conversion efficiencies in the 0.1-1 % order of magnitude; metrics which are comparable with those reported for spin-coated cells of the same active blend and device architecture.authorsversionPeer reviewe

Optically Transparent Protective Coating for Plastics Using Dual Spray and Atmospheric Plasma Deposition

“…With optimized spraying condition (described in the “Experimental Section”), the base adhesive layer was spray coated at a deposition rate of ≈400 nm min −1 . Fast deposition is important for industrial upscaling and the deposition rate reported here is comparable to the values found in literatures . For adhesive layer with different TPOZ‐GPTMS compositions, the deposition rates were found to decrease slightly with increasing TPOZ content.…”

Overview of printing and coating techniques in the production of organic photovoltaic cells

“…On the other hand, if the distance is small, the film will be moist and with holes. 11,117,118 Thus, in order to obtain a homogeneous and without holes film, one must "To choose a fast drying solvent to prevent droplets from redissolving sublayers but not so fast so as to allow for a homogenous and pin-hole free film to form." 119 Spray coating has been used in several reports in the literature to prepare many of the layers OPV, Vak et al 45 used the spray coating in the deposition of the active layer (P3HT:PCBM) and stated that this technique provides control of the film thickness similar to the control done in vacuum deposition.…”

“…Regarding the distance between the nozzle and the substrate, if the distance is large, the solvent will evaporate along the way to the substrate, causing a dry film. On the other hand, if the distance is small, the film will be moist and with holes 11,117,118 . Thus, in order to obtain a homogeneous and without holes film, one must “To choose a fast drying solvent to prevent droplets from redissolving sublayers but not so fast so as to allow for a homogenous and pin‐hole free film to form.” 119 …”

Spray-coating deposition techniques for polymeric semiconductor blends

“…Adjustable experimental parameters are flow rate, solvent (and hence viscosity), material concentration, nozzle-substrate distance (X), substrate temperature. In terms of the optimal solvent media parameters for deposition of these materials, we adopt the approach of Noebels et al [13], using a solvent mixture of low viscosity chlorinated-aromatic solvents. We find that the optimal conditions of droplet size, solution transfer, substrate adhesion, and film formation can be obtained using a mixture of chlorobenzene(CB) and dichloro-benzene(DCB) in a 1:5 ratio (all solvents from Sigma-Aldrich); this solvent medium has a measured dynamic viscosity of 1.22 cP.…”

“…Some attempts at using spray-coated active layers in polymeric transistors and field-effect transistors are also reported [12]. However, the main apparent drawback of this method is the roughness of the surface after coating, as illustrated by our earlier studies of polyfluorene photovoltaic blends [13]; the droplets formed in spray atomization translate into crater-like (or "craterform") structures in films on substrates, with relatively flat central areas and markedly raised edges or "walls". Of a particular prescience, the engineering tolerance of active layer thicknesses in organic optoelectronics range from a maximum of 1 micron for LEDs [14] down to sub-100nm in virtually all feasible solar cell designs.…”