Organic photovoltaics (OPVs) that perform more efficiently under artificial indoor lighting conditions than they do under sunlight are attracting growing interest as they can potentially serve as ambient energy harvesters for powering low-power electronics and portable devices for the Internet of Things. Herein, solution-processed small-molecule OPVs are demonstrated to exhibit high power conversion efficiencies exceeding 16% under white LED illumination, delivering high output power densities of up to 12.4 and 65.3 μW cm–2 at 200 and 1000 lx, respectively. Increasing the open-circuit voltage (V oc) of OPVs is a critical factor for achieving higher indoor photovoltaic performance. Toward real applications, this small-molecule OPV system is adopted to fabricate six series-connected modules with an active area of ∼10 cm2 that are capable of generating a high output power surpassing 100 μW and a high V oc of over 4.2 V even under dimly lit indoor conditions of 200 lx. These results indicate that OPVs are promising as indoor electric power sources for self-sustainable electronic devices.

Full-color all-organic optical upconversion devices that can directly convert incident near-infrared (NIR) light into tunable visible light were developed by integrating an organic light-emitting diode (OLED) on an NIR-sensitizing organic photodetector. Thermally activated delayed fluorescence (TADF) emitters were utilized for the first time in the upconversion devices for achieving high electroluminescence (EL) efficiency in the OLED unit and high overall upconversion efficiency. The emission color of upconversion EL can be varied across the entire visible region ranging from blue to red and white by judicious selection of the incorporating TADF emitters. These all-organic optical upconversion devices have a great potential for low-cost, large-area, pixelless NIR imaging applications.

high-cost, brittle silicon-based solar cells are widely used, great research efforts are being devoted to produce cost-effective and high-effi ciency solar cells as nextgeneration ubiquitous energy-harvesting devices. [ 1,2 ] Solution-processed organic solar cells (OSCs) based on bulk heterojunction (BHJ) structures incorporating narrow-bandgap π-conjugated molecules as a donor and fullerene derivatives as an acceptor have been intensively investigated thus far because of their advantages such as light weight, fl exibility, potential for mass production and low energy consumption during manufacturing. [ 3 ] As a result of rapid advancements in both semiconducting materials and device architectures, high power conversion effi ciencies (PCEs) surpassing 9% have been reported recently for polymer BHJ OSCs. [ 4 ] Over the past few years, solution-processable narrow-bandgap small molecules have gained increasing attention because of their advantages, such as defi ned molecular structure, intrinsic monodispersity, high purity, negligible batch-to-batch variations, and reproducible performance, compared to conventional polymer counterparts. [ 5 ] The PCEs of state-of-the-art small-molecule BHJ OSCs have exceeded 7%, [ 6 ] approaching those of the best-performing polymer OSCs. Despite the foregoing potential benefi ts, the typical backbone structures for A series of narrow-bandgap π-conjugated oligomers based on diketopyrrolopyrrole chromophoric units coupled with benzodithiophene, indacenodithiophene, thiophene, and isoindigo cores are designed and synthesized for application as donor materials in solution-processed small-molecule organic solar cells. The impacts of these different central cores on the optoelectronic and morphological properties, carrier mobility, and photovoltaic performance are investigated. These π-extended oligomers possess broad and intense optical absorption covering the range from 550 to 750 nm, narrow optical bandgaps of 1.52-1.69 eV, and relatively low-lying highest occupied molecular orbital (HOMO) energy levels ranging from −5.24 to −5.46 eV in their thin fi lms. A high power conversion effi ciency of 5.9% under simulated AM 1.5G illumination is achieved for inverted organic solar cells based on a small-molecule bulk-heterojunction system consisting of a benzodithiophene-diketopyrrolopyrrole-containing oligomer as a donor and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) as an acceptor. Transmission electron microscopy and energy-dispersive X-ray spectroscopy reveal that interpenetrating and interconnected donor/acceptor domains with pronounced mesoscopic phase segregation are formed within the photoactive binary blends, which is ideal for effi cient exciton dissociation and charge transport in the bulk-heterojunction devices.

Solution-processed organic solar cells (OSCs) based on narrow-band gap small molecules hold great promise as next-generation energy-converting devices. In this paper, we focus on a family of A-π-D-π-A-type small molecules, namely, BDT- nT-ID ( n = 1-4) oligomers, consisting of benzo[1,2- b:4,5- b']dithiophene (BDT) as the central electron-donating (D) core, 1,3-indandione (ID) as the terminal electron-accepting (A) units, and two regioregular oligo(3-hexylthiophene)s ( nT) with different numbers of thiophene rings as the π-bridging units, and elucidate their structure-property-function relationships. The effects of the length of the π-bridging nT units on the optical absorption, thermal behavior, morphology, hole mobility, and OSC performance were systematically investigated. All oligomers exhibited broad and intense visible photoabsorption in the 400-700 nm range. The photovoltaic performances of bulk heterojunction OSCs based on BDT- nT-IDs as donors and a fullerene derivative as an acceptor were studied. Among these oligomers, BDT-2T-ID, incorporating bithiophene as the π-bridging units, showed better photovoltaic performance with a maximum power conversion efficiency as high as 6.9% under AM 1.5G illumination without using solvent additives or postdeposition treatments. These favorable properties originated from the well-developed interpenetrating network morphology of BDT-2T-ID, with larger domain sizes in the photoactive layer. Even though all oligomers have the same A-D-A main backbone, structural modulation of the π-bridging nT length was found to impact their self-organization and nanostructure formation in the solid state, as well as the corresponding OSC device performance.

C-Linked carbohydrate structure, in which the cleavable O-glycosidic linkage is replaced by a carbon unit, is a useful tool for functional analyses of glycoconjugates. We describe a synthetic method for α-CH 2 -linked disaccharide structures, such as Glc(1,6)-Glc, by stereoselective radical-coupling C-glycosylation between a conformationally constrained and stable C1-sp 3 hybridized xanthate donor and a carefully designed acceptor.

Direct C-glycosylation of a conformationally constrained and stable C1-sp3 hybridized carbohydrate donor with a carefully designed sphingosine unit afforded the CH2-linked analogue of antitumor-active KRN7000 and its glucose congener.

High‐efficiency solution‐processed organic solar cells based on narrow‐bandgap π‐conjugated oligomers are demonstrated by Takuma Yasuda, Chihaya Adachi, and co‐workers in article number 1400879. Well‐organized donor/acceptor bulk‐heterojunction domains with pronounced mesoscopic phase segregation are spontaneously formed in a photoactive binary blend layer. A high power conversion efficiency of 5.9% is achieved for small‐molecule organic solar cells.