Despite the success of thermally activated delayed fluorescent (TADF) materials in steering the next generation of organic light-emitting diodes (OLEDs), effective near infrared (NIR) TADF emitters are still very rare. Here, we present a simple and extremely high electron-deficient compound, 5,6dicyano[2,1,3]benzothiadiazole (CNBz), as a strong electronaccepting unit to develop a sufficiently strong donor-acceptor (DÀ A) interaction for NIR emission. End-capping with the electron-donating triphenylamine (TPA) unit created an effective DÀ AÀ D type system, giving rise to an efficient NIR TADF emissive molecule (λ em = 750 nm) with a very small ΔE ST of 0.06 eV. The electroluminescent device using this NIR TADF emitter exhibited an excellent performance with a high maximum radiance of 10020 mW Sr À 1 m À 2 , a maximum EQE of 6.57% and a peak wavelength of 712 nm.

Perovskite solar cells (PSCs) have received high attention in the past few years due to their terrific photovoltaic performance and potentially low production cost. However, the use of hole transport materials (HTMs) with hygroscopic dopants, which cause the inevitable instability of device performance, has hampered commercialization. Herein, a dopant-free polymeric HTM with functional aromatic rings was used to optimize the HTM/perovskite interface and employed in a planar n-i-p configuration. Poly(1,4-(2,5-bis((2-butyloctyloxy)phenylene)-2,7-(5,5,10,10-tetrakis(4-hexylphenyl)-5,10-dihydro-s-indaceno[2,1b:6,5-b']dithiophene)) (IDTB) co-polymer constructed with indaceno[1,2-b:5,6-b']dithiophene and bis(alkyloxy)benzene units adopts an S•••O intramolecular bond linked ladder-like planar conjugated polymer backbone. Without any dopant, the hole mobility of IDTB is in the same order of magnitude as a doped 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD). Also, the hydrophobic nature of IDTB facilitated the long-term stability of the perovskite underneath. The unencapsulated PSC devices made of IDTB-based HTM achieved a power conversion efficiency of 19.38 % with a high moisture stability, retaining above 80 % of initial power conversion efficiency at 65 % relative humidity for more than 10 days. The superior passivation effect to perovskite surface made a hysteresis of 0.44 % was almost the least reported for regular planar undoped polymer HTM PSCs.

The hybridized local and charge-transfer (HLCT) excited state is a successful strategy to produce both high external and internal quantum efficiency. Based on HLCT scheme, two isomeric donor-acceptor (D-A) type...

Herein, two new triplet-triplet annihilation (TTA) molecules, namely HO-PIAC and PIAC, as deep blue emitters for high-efficiency TTA-OLEDs are designed and synthesized. HO-PIAC and PIAC contain 4-(N-phenylcarbazol-3-yl)phenylanthracene as a blue...

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