RESUMO
The intractable brittleness and opacity of the crystalline semiconductor restrict the prospect of developing low-cost imaging systems. Here, infrared visualization technologies are established with large-area, semi-transparent organic upconversion devices that bring high-resolution invisible images into sight without photolithography. To exploit all photoinduced charge carriers, a monolithic device structure is proposed built on the infrared-selective, single-component charge generation layer of chloroaluminum phthalocyanine (ClAlPc) coupled to two visible light-emitting layers manipulated with unipolar charges. Transient pump-probe spectroscopy reveals that the ClAlPc-based device exhibits an efficient charge dissociation process under forward bias. This process is indicated by the prompt and strong features of electroabsorption screening. Furthermore, by imposing the electric field, the ultrafast excited state dynamic suggests a prolonged charge carrier lifetime from the ClAlPc, which facilitates the charge utilization for upconversion luminance. For the first time, >30% of the infrared photons are utilized without photomultiplication strategies owing to the trivial spectrum overlap between ClAlPc and the emitter. In addition, the device can broadcast the acoustic signal by synchronizing the device frequency with the light source, which enables to operate it in dual audio-visual mode. The work demonstrates the potential of upconversion devices for affordable infrared imaging in wearable electronics.
RESUMO
Crystalline photodiodes remain the most viable infrared sensing technology of choice, yet the opacity and the limitation in pixel size reduction per se restrict their development for supporting high-resolution in situ infrared images. In this work, we propose an all-organic non-fullerene-based upconversion device that brings invisible infrared signal into human vision via exciplex cohost light-emissive system. The device reaches an infrared-to-visible upconversion efficiency of 12.56% by resolving the 940-nm infrared signal (power density of 103.8 µW cm-2). We tailor a semitransparent (AVT, ~60%), large-area (10.35 cm2), lightweight (22.91 g), single-pixel upconversion panel to visualize the infrared power density down to 0.75 µW cm2, inferring a bias-switching linear dynamic range approaching 80 dB. We also demonstrate the possibility of visualizing low-intensity infrared signals from the Face ID and LiDAR, which should fill the gap in the existing technology based on pixelated complementary metal-oxide semiconductors with optical lenses.
RESUMO
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.
