A Near‐Infrared Absorption Small Molecule Acceptor for High‐Performance Semitransparent and Colorful Binary and Ternary Organic Photovoltaics

An acceptor–donor–acceptor (A–D–A)‐type non‐fullerene acceptor (NFA), PTTtID‐Cl, featuring thieno[3,2‐ b ]thieno[2′′′,3′′′:4′′,5′′]‐pyrrolo[2′′,3′′:4′,5′]thieno[2′,3′:4,5]thieno‐[2,3‐ d ]pyrrole (DTPTt) as the electron‐rich core and 2‐(5,6‐dichloro‐3‐oxo‐2,3‐dihydro‐1 H ‐inden‐1‐ylidene)malononitrile (ID‐Cl) as the peripheral electron‐deficient terminal group was synthesized and characterized. PTTtID‐Cl exhibited strong absorption in the range of 700–850 nm in CHCl 3 and redshifted absorption centered at 881 nm in a thin film. The near infrared (NIR)‐absorption of PTTtID‐Cl was combined with a low‐bandgap polymer donor (PTB7‐Th) to achieve binary and semitransparent organic photovoltaics (OPVs) with a power conversion efficiency (PCE) of 8.9 % and 7.7 % (with an average visible transmittance (AVT) of 16.7 %), respectively. A ternary device with a ratio of PM7/PTTtID‐Cl/IT‐4F=1:0.15:0.85 ( w / w ) achieved a short‐circuit current density of 19.46 mA cm −2 , an open‐circuit voltage of 0.87 V, and a fill factor of 71.2 %, giving a PCE of 12.0 %. In addition, by employing the Ag/ITO/Ag microcavity structure, semitransparent colorful binary organic photovoltaics (OPVs) with superior transparency of 27.9 % at 427 nm and 22.7 % at 536 nm for blue and green devices, respectively, were prepared. The semitransparent colorful devices based on the optimized ternary blend gave PCEs of 8.7 %, 8.4 %, and 9.1 % for blue, green, and red devices, respectively. These results indicate the promising potential of PTTtID‐Cl as a NIR‐absorption NFA for applications in semitransparent colorful binary and ternary OPVs.