Donor-Acceptor Type Molecules for High Performance Green-Light-Selective Organic Photodiodes

The specific properties of organic semiconductors, such as the color tenability, mechanical flexibility, and low-cost process-ability, have attracted interest for future optoelectronic device applications.In particular, the dipolar donor (D)–acceptor (A) approach is a representative and powerful strategy to design the wavelength-selective organic absorbers, as the optical and electrical properties of the D–A type materials can be tuned using an appropriate combination of D and A moieties.Herein we report dipolar donor (D)-π-acceptor (A) molecules for application to green-light-selective organic photodiodes (OPDs). Novel p-type molecules combined with two types of fused heterocyclic donors and an electron-accepting unit has been synthesized and characterized. The molecules exhibit cyanine-like properties that are characterized by intense and sharp absorption. This molecular design leads to improved absorption properties, thermal stability, and higher photoelectric conversion compared to those of a molecular design based on a non-fused ring. A maximum external quantum efficiency of 66% (λ_max = 550 nm) and high specific detectivity (D*) of 8 × 10¹³ cm Hz^1/2/W are achieved in an OPD consisting of a bulk heterojunction blend of the p-type molecule and fullerene (C₆₀). Finally, the green-light-detection capability of the green-selective OPD is demonstrated by the optical simulation of a stacked-type organic-on-Si hybrid full-color photodetector comprising the green-light-selective OPD and a bottom Si photodiode with only blue and red color filters.