Morphology Inversion of a Non‐Fullerene Acceptor Via Adhesion Controlled Decal‐Coating for Efficient Conversion and Detection in Organic Electronics
Min Soo Kim, Woongsik Jang, Thuc‐Quyen Nguyen, Dong Hwan Wang
Abstract
Abstract In this study, a promising film formation technique is highlighted, named mold‐assisted decal‐coating, as a thin film transfer printing process using the polyurethane acrylate‐based stamping mold. By optimizing the surface energy of the mold with wetting coefficient theory, the mold‐assisted decal‐coating process is successfully demonstrated by transferring the photoactive layer composed of the polymer donor, poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐ b ;4,5‐ b ′]dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐ b ]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)] and a narrow bandgap non‐fullerene acceptor (NFA), 2,2′‐[[4,4,9,9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐s‐indaceno[1,2‐ b :5,6‐ b ′]dithiophene‐2,7‐diyl]bis[[4‐[(2‐ethylhexyl)oxy]‐5,2‐thiophenediyl]methylidyne(5,6‐difluoro‐3‐oxo‐1H‐indene‐2,1(3H)‐diylidene)]]bis[propanedinitrile]. This process induces a well‐ordered morphology of photoactive material, prevents damage to the underlying layer by suppressing the solvent penetration. Both photovoltaic cells and photodetectors prepared by the decal‐coated photoactive layers containing fluorinated NFAs showed higher performance (power conversion efficiency = 10.69% and specific detectivity = 1.27 × 10 12 A cm Hz 1/2 W −1 , respectively) than those of cells prepared by the spin‐coating method owing to morphology inversion and smoother interface that led to suppressed internal resistance and enhanced charge flow in normal structure. Thus, the reproducible decal‐coating process using a customized elastomeric mediator is an important thin film coating technique for efficient next‐generation organic optoelectronic materials.