The design of circuits utilizing organic complementary metal oxide semiconductor (CMOS) architecture requires the development of both p-channel and n-channel semiconductors with high performance and air-stability. Compared to highly developed p-channel organic semiconductors, the availability of high-performance, air-stable n-channel materials, in particular with solution processability, remains considerably limited. 1 This is attributed to the vulnerability of electrons to trapping by ambient oxidants, such as O 2 and H 2 O. 2 These ambient traps result in significant decreases of the density of mobile electrons in n-channel organic thin-film transistors (OTFTs) and, thus, poor airstability. The difficulties encountered in the development of new, airstable n-channel semiconductors prompted us to seek a new approach to increase the density of mobile electrons to compensate for the trapped electrons under ambient conditions. We hypothesized that controlled n-type doping might fulfill this requirement. Previous attempts at intentional doping have increased film conductivities as a result of increased charge carrier density, 3 with the approach resulting in highly efficient organic light-emitting diodes (OLEDs) 4 and organic photovoltaics (OPVs). 5 However, the design of n-type (vs p-type) dopants is considerably challenging owing to the requirement of highlying dopant highest occupied molecular orbital (HOMO) levels, making n-type dopants unstable against O 2 . 3e A promising strategy involves the formation of the active dopant species through thermal activation or photoactivation, allowing the active n-type dopants to transfer electrons to the host matrix and form stable cations. 3b,d However, most previously reported dopants were processed by vacuum deposition and required high conversion temperatures. These dopants were thus incompatible with solution-processed materials and demonstrated weak doping effects (i.e., insufficient to render the device air-stable). Therefore, it is essential to design new n-type dopants for solution-processed n-channel OTFTs.1,3-Dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole (DMBI) derivatives have been reported as effective reagents for reductive transformations of organic compounds. 6 These materials are also known to promote hydrogen-and/or electron-transfer reactions via radical formation. 7 Thus, these solution-processable moieties present an ideal class of n-type dopants, as they readily form neutral radicals and H radical. 6 In this Communication, we report the use of (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI, Figure 1a) as an n-type dopant and demonstrate improved airstability of N-DMBI-doped n-channel OTFTs by solution processing.To characterize the doping effect of N-DMBI, film conductivities of a well-known solution-processable n-channel semiconductor, [6,6]-phenyl C 61 butyric acid methyl ester (PCBM), 8 were explored. N-DMBI and PCBM were mixed at varying ratios and spin-coated from chlorobenzene solutions to form thin films. Th...

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Using imidazole‐type ancillary ligands, a new class of cationic iridium complexes (1–6) is prepared, and photophysical and electrochemical studies and theoretical calculations are performed. Compared with the widely used bpy (2,2′‐bipyridine)‐type ancillary ligands, imidazole‐type ancillary ligands can be prepared and modified with ease, and are capable of blueshifting the emission spectra of cationic iridium complexes. By tuning the conjugation length of the ancillary ligands, blue‐green to red emitting cationic iridium complexes are obtained. Single‐layer light‐emitting electrochemical cells (LECs) based on cationic iridium complexes show blue‐green to red electroluminescence. High efficiencies of 8.4, 18.6, and 13.2 cd A−1 are achieved for the blue‐green‐emitting, yellow‐emitting, and orange‐emitting devices, respectively. By doping the red‐emitting complex into the blue‐green LEC, white LECs are realized, which give warm‐white light with Commission Internationale de L'Eclairage (CIE) coordinates of (0.42, 0.44) and color‐rendering indexes (CRI) of up to 81. The peak external quantum efficiency, current efficiency, and power efficiency of the white LECs reach 5.2%, 11.2 cd A−1, and 10 lm W−1, respectively, which are the highest for white LECs reported so far, and indicate the great potential for the use of these cationic iridium complexes in white LECs.

The two-dimensional Ruddlesden-Popper (RP) phases are an important class of halide perovskites with versatile optoelectronic properties. So far, only organic-inorganic hybrid RP phases involving long organic spacers were reported in this class. Here, we report an all-inorganic RP phase lead halide perovskite, CsPbICl (1, I4/ mmm space group; a = 5.6385(8) Å, c = 18.879(4) Å), synthesized by a solid-state method. The compound exhibits a band gap of E ∼ 3.04 eV and photoconductivity. We find an anomalous band gap evolution in CsPbSn ICl solid solutions. Our combined density functional theory and experimental study supports the thermodynamically stable nature of 1 as a unique ordered phase in the CsPbX (X = Cl, Br, I) system. The calculations suggest that 1 is a direct bandgap semiconductor with relatively small effective carrier mass along the in-plane direction, consistent with the experimentally observed in-plane UV-light photoresponse. We also demonstrate that 1 is promising for radiation detection capable of α-particle counting. Moreover, 1 shows markedly ambient and thermal stability.