pH-Induced antireflection coatings derived from hydrogen-bonding-directed multilayer films.

Hydrogen-bonding-directed layer-by-layer assembled films, based on polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles and poly(4-vinylpyridine) (P4VP), were successfully fabricated in methanol. Varying the PAA content in the PS-b-PAA micelles afforded control over the film growth properties, especially the multilayer film thickness. Interestingly, antireflection films with refractive indices that could be tuned between 1.58 and 1.28 were obtained by treatment with an aqueous HCl solution (pH 2.27), and the transmittance obtained was as high as 98.4%. In acid solution, the pyridine group was protonated, destroying the hydrogen bonding between P4VP and PAA. A concomitant pH-induced polymer reorganization in the multilayers resulted in a porous honeycomb-like texture on the substrate.

Controlled nanomorphology of PCDTBT-fullerene blends via polymer end-group functionalization for high efficiency organic solar cells.

We propose a novel method for the control of nanoscale morphologies of the photoactive layers of organic solar cells by using end group functionalization of p-type polymers. The devices based on the end-fluorinated PCDTBT exhibit a remarkably enhanced efficiency as high as 6.0% without applying any post-treatments, additives or optical spacers.