Effective multimodality phototheranostics under deep-penetration laser excitation is highly desired for tumor medicine, which is still at a deadlock due to lack of versatile photosensitizers with absorption located in the long-wavelength region. Herein, we demonstrate a stable organic photosensitizer nanoparticle based on molecular engineering of benzo[c]thiophene (BT)-based photoactivated molecules with strong wavelength-tunable absorption in the near-infrared region. Via molecular design, the absorption and singlet oxygen generation of BT molecules would be reliably tuned. Importantly, the nanoparticles with a red-shifted absorption peak of 843 nm not only show over 10-fold reactive oxygen species yield compared with indocyanine green but also demonstrate a notable photothermal effect and photoacoustic signal upon 808 nm excitation. The in vitro and in vivo experiments substantiate good multimodal anticancer efficacy and imaging performance of BT theranostics. This work provides an organic photosensitizer nanoparticle with long-wavelength excitation and high photoenergy conversion efficiency for multimodality phototherapy.

Two new spirobifluorene (SF)‐centered donors (D) DPSF and DTSF are developed to blend with acceptor (A) CN‐T2T for exciplex formation. The transient photoluminescence characterizations of pristine donor and D:A blended films verify the donor aggregates emissions that lead to relatively low photoluminescence quantum yield (PLQY) of exciplex emission. However, the charge recombination at lower energy exciplex state leads the device with DPSF:CN‐T2T blend to give electroluminescence (EL) λmax of 584 nm and external quantum efficiency (EQE) of 6.0%. The DPSF:CN‐T2T exciplex excitons are efficiently extracted by a D‐A‐D‐type fluorescence emitter TTDSF comprising thienothiadiazole core and SF peripherals via Förster energy transfer to give near‐infrared (NIR) emission (760 nm, PLQY 26%). After the electron‐transporting layer thickness optimization, the device with DPSF:CN‐T2T: 7 wt.% TTDSF as emitting layer affords EL λmax 774 nm and EQE up to 5.3%, one of the best cases in NIR organic light‐emitting diodes (OLEDs). More importantly, the device stability has been examined to display an excellent lifetime (LT95 > 200 hours). This work manifests the judicious combination of an exciplex‐forming co‐host system and a designated NIR emitter equipping with a high quinoidal core and rigid peripheral SF groups that can realize an efficient NIR OLED.

Three triazatruxene-based donors Tr-Me, Tr-Ph, and Tr-Tol were intermixed with three acceptors 3P-T2T, 3P-T2P, and 3P-Pyr equipping with different heteroarene cores to generate an array of nine blends to probe the feasibility of exciplex formation.

Three new carbazole-based materials were designed for exciplex formation with PO-T2T. Then, the selected exciplex cohost two D–A–D-configurated fluorescent emitters, iCzPNT and iCzBTh2CN, to produce high efficiency OLEDs.