A near‐infrared photodetector with optimized performance is reported using varied thickness (20, 40, 60, and 80 nm) of the active layer comprising chloroaluminium phthalocyanine (ClAlPc) and fullerene (C70) at the ratio of 1:3, and TAPC:10% MoO3 and BPhen as electron and hole blocking layers, respectively. The experimental results reveal that the photodetector with 80 nm thick active layer provides the best performance at the wavelength of 730 nm achieving a very low dark current density of 1.15 × 10−9 A cm−2 and an external quantum efficiency of 74.6% with a responsivity of 0.439 A W−1 at −2 V bias. Additionally, the device exhibits a dramatic high detectivity of 4.14 × 1013 cm Hz1/2 W−1 at 0 V bias. The device exhibits not only a large linear response over a wide optical power range (LDR of 173.0 dB), but also a broad frequency response (778.7 kHz) and rise/fall time of 2.13/0.77 µs (based on trigger pulses at a frequency of 10 kHz) at the applied bias of −2 V. Based on the impedance spectroscopic study and the conventional characterization of electro‐optical properties, the results demonstrate the superiority of this device over other small molecule‐based near‐infrared photodetectors.

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Four new donor–acceptor–acceptor (D–A–A) type molecules (DTCPB, DTCTB, DTCPBO, and DTCTBO), wherein benzothiadiazole or benzoxadiazole serves as the central A bridging triarylamine (D) and cyano group (terminal A), have been synthesized and characterized. The intramolecular charge-transfer character renders these molecules with strong visible light absorption and forms antiparallel dimeric crystal packing with evident π–π intermolecular interactions. The characteristics of the vacuum-processed photovoltaic device with a bulk heterojunction active layer employing these molecules as electronic donors combining C70 as electronic acceptor were examined and a clear structure–property–performance relationship was concluded. Among them, the DTCPB-based device delivers the best power conversion efficiency (PCE) up to 6.55% under AM 1.5 G irradiation. The study of PCE dependence on the light intensity indicates the DTCPB-based device exhibits superior exciton dissociation and less propensity of geminated recombination, which was further verified by a steady photoluminescence study. The DTCPB-based device was further optimized to give an improved PCE up to 6.96% with relatively high stability under AM 1.5 G continuous light-soaking for 150 h. This device can also perform a PCE close to 16% under a TLD-840 fluorescent lamp (800 lux), indicating its promising prospect for indoor photovoltaic application.

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