Chengyuan Wang

Synthesis, characterization, and nonvolatile ternary memory behavior of a larger heteroacene with nine linearly fused rings and two different heteroatoms.

To achieve ultrahigh density memory devices with the capacity of 3(n) or larger, organic materials with multilevel stable states are highly desirable. Here, we reported a novel larger stable heteroacene, 2,3,13,14-tetradecyloxy-5,11,16,22-tetraaza-6,10,17,21-tetrachloro-7,9,18,20-tetraoxa-8,19-dicyanoenneacene (CDPzN), which has two different types of heteroatoms (O and N) and nine linearly fused rings. The sandwich-structure memory devices based on CDPzN exhibited excellent ternary memory behaviors with high ON2/ON1/OFF current ratios of 10(6.3)/10(4.3)/1 and good stability for these three states.

Synthesis, Structure, and Air‐stable N‐type Field‐Effect Transistor Behaviors of Functionalized Octaazanonacene‐8,19‐dione

Increasing the length of N-heteroacenes or their analogues is highly desirable because such materials could have great potential applications in organic electronics. In this report, the large π-conjugated N-heteroquinone 6,10,17,21-tetra-((triisopropylsilyl)ethynyl)-5,7,9,11,16,18,20,22-octaazanonacene-8,19-dione (OANQ) has been synthesized and characterized. The as-prepared OANQ shows high stability under ambient conditions and has a particularly low LUMO level, which leads to it being a promising candidate for air-stable n-type field-effect transistors (FETs). In fact, FET devices based on OANQ single crystals have been fabricated and an electron mobility of up to 0.2 cm(2) V(-1) s(-1) under ambient conditions is reported. More importantly, no obvious degradation was observed even after one month. Theoretical calculations based on the single crystal are consistent with the measured mobility.

Synthesis and Physical Properties of Four Hexazapentacene Derivatives

In two steps from commercially available starting materials, four novel hexazapentacene derivatives have been synthesized through cyclocondensation reaction between tetraamines and 1,2-diketones. The observed optical bandgaps for 2,3,9,10-tetramethyl-1,4,6,8,11,13-hexaza-pentacene (TMHAP, 1), tetraethyl-1,4,6,8,11,13-hexaza-pentacene (TEHAP, 2), 1,2,3,4,10,11,12,13-octahydro-5,7, 9,14,16,18-hexazaheptacene (OHHAH, 3), and tetra(2-thioyl)-1,4,6,8,11,13-hexazapentacene (TTHAP, 4) are 2.55, 2.55, 2.45, and 2.25 eV, respectively. The cyclic voltammetry measurements show that all compounds exhibit one revisable reduction waves. The calculated bandgaps through DFT calculations for TMHAP (1), TEHAP (2), OHAH (3), and TTHAP (4) are 2.41, 2.41, 2.34, and 2.15 eV, respectivly, which are close to the experimental results. Our success in synthesizing hexazapentacene derivatives might offer a promising strategy to challenge larger azaacenes with more N atoms.

Recent progress in organic resistance memory with small molecules and inorganic–organic hybrid polymers as active elements

Organic resistance memory has attracted a lot of attention due to its high scalability, flexibility, easy processing, low fabrication cost, etc. Organic small molecules, which possess well-defined structures and more accurate experiment-simulation matching, have been widely explored as active materials for application in organic resistance memory. In addition, inorganic–organic hybrid polymers are expected to have charming resistive switching properties because they can potentially combine the advantages of both inorganic materials and organic polymers. This review presents the recent progress of organic resistance memory based on several families of organic small molecules and some typical inorganic–organic hybrid polymers, and discussion of their structure–property relationships.

Inorganic–organic hybrid polymer with multiple redox for high-density data storage

Although organic multilevel resistance memories have attracted much attention for potential realization of the exponentially-increasing density of data storage, the ambiguous structure–property relationship and the unclear switching mechanism impeded further development of multilevel resistance memory devices. Therefore, it is very urgent to ingeniously design multilevel memory materials with a certain switching mechanism. In this contribution, we have employed a multi-redox (multiple barriers) polyoxometalate-based inorganic–organic hybrid polymer (whose effective carriers are electrically controllable) to realize a ternary resistance switching memory (multilevel memories). We do believe that the as-designed inorganic–organic polymer can integrate the multi-redox states of the POM and the processability of flexible polymers together. The as-fabricated multilevel memory devices exhibit rewriteable switching properties among three redox states by applying different RESET voltages, good endurance with distinct operation windows, and long retention. Our results could provide a new strategy to design controllable multilevel resistance memories with excellent performance.

Synthesis and nonvolatile memory behaviors of dioxatetraazapentacene derivatives.

Two novel heteroacenes 2,3,9,10-tetra(furan-2-yl)-1,4,8,11-tetraaza-6,13-dioxapentacene (FAOP, 1) and 2,3,9,10-tetra(thiophen-2-yl)-1,4,8,11-tetraaza-6,13-dioxapentacene (TAOP, 2) was successfully synthesized through a one-step condensation reaction, which have been fully characterized by (1)H NMR (nuclear magnetic resonance), (13)C NMR, FT-IR (Fourier transform infrared spectroscopy), and HRMS (high-resolution mass spectrum). The sandwich-structure memory devices have been fabricated using FAOP (1) and TAOP (2) as active layers, showing a typical bipolar resistive switching (RS) behavior in positive and negative regions.

Synthesis, physical properties, and light-emitting diode performance of phenazine-based derivatives with three, five, and nine fused six-membered rings.

Realizing the control of emission colors of single molecules is very important in the development of full-color emitting materials. Herein, three novel phenazine derivatives (2,3,7,8-tetrakis(decyloxy)phenazine (2a), 2,3-didecyloxy-5,14-diaza-7,12-dioxo-9,10- dicyanopentacene (2b), and 2,3,13,14-tetradecyloxy-5,11,16,22-tetraaza-7,9,18,20-tetraoxo-8,19-dicyanoenneacene (2c)) have been successfully synthesized and fully characterized. Compound 2c can emit blue light in toluene solution (450 nm), green light in the powder/film state (502/562 nm), and red light in the 2c/TFA state (610 nm). The OLED with 2c emits a strong green light at a peak of 536 nm with a maximum luminance of the OLED of about 8600 cd m(-2), which indicates that 2c could be a promising fluorescent dye for OLED applications.

Pushing up the efficiency of planar perovskite solar cells to 18.2% with organic small molecules as the electron transport layer

Compared to the traditional-architecture perovskite photovoltaic solar cells (n-i-p type), which use metal oxide as electron transport layers (ETLs) and organic semiconducting materials as hole transport layers, the fabrication of metal-oxide-free, solution-processed inverted perovskite solar cells (PSCs) is more desired because of low-temperatures and all-solution-based applications in future commercial PSC modules. In a typical configuration of inverted PSCs, the widely used ETL compound is the fullerene-based phenyl-C61-butyric acid methyl ester (PCBM), which currently is the best organic ETL material. The cost of this compound is very high, and the morphology and electrical properties are very sensitive to experimental conditions. We here propose a new organic ETL material for the replacement of PCBM in inverted PSCs. We demonstrate metal-oxide-free solution-processed inverted PSCs using the n-type sulfur-containing azaacene 10,14-bis(5-(2-ethylhexyl)thiophen-2-yl)-dipyrido[3,2-a:2′,3′-c][1,2,5]thiadiazolo[3,4-i]phenazine (TDTP) as the ETL with a power conversion efficiency of ∼18.2%, which is higher than that of the corresponding non-sulfur-containing azaacene 10,17-bis((triisopropylsilyl)ethynyl)dipyrido[3,2-a:2′,3′-c]quinoxalino[2,3-i]phenazine (PYPH)-based PSCs (up to 9.5%) or PCBM-based PSCs (up to 17.0%). This superior performance is attributed to the stronger interaction between TDTP and the perovskite surface than that between PYPH and the perovskite surface, which is supported by theoretical calculations. Our results show that easily-accessible simple n-type sulfur-containing small molecules are promising ETL candidates to further propel inverted PSCs to practical applications.

Synthesis, physical properties, and self-assembly of a novel asymmetric aroyleneimidazophenazine.

The synthesis, physical properties, and self-assembly of a novel asymmetric aroyleneimidazophenazine (IZ1) is reported. The as-prepared IZ1 nanowires display an obvious red fluorescence. A heterojunction light-emitting diode (LED) device with the structure ITO/IZ1 nanowires/p-SiC/Al (10 nm)/Ti (80 nm)/Al (380 nm)/ITO was fabricated, and electroluminescence emission with two peaks at about 412 nm and 613 nm was detected with a forward bias ranging from 5 to 10 V.

Inorganic–Organic Hybrid Nanoprobe for NIR-Excited Imaging of Hydrogen Sulfide in Cell Cultures and Inflammation in a Mouse Model

Hydrogen sulfide (H2S) is an important gaseous signaling agent mediated by many physiological processes and diseases. In order to explore its role in biological signaling, much effort has been focused on developing organic fluorescent probes to image H2S. However, these downconversion H2S probes are impractical for bio-imaging beyond a certain depth because of the short tissue penetration of UV/visible light (as an excitation source). In most circumstance, these probes are also not suitable for long-term assay due to photo-bleaching. Herein, a new design to detect H2S based on the coumarin-hemicyanine (CHC1)-modified upconversion nanophosphors is reported. This inorganic-organic integrated nanoprobe is demonstrated to display a fast response time with a large ratiometric upconversion luminescence (UCL) enhancement, and extraordinary photo-stability. CHC1-UCNPs not only can be used for ratiometric UCL monitoring of pseudo-enzymatic H2S production in living cells, but can also be used to identify the risk of endotoxic shock through ratiometric UCL imaging of tissue and measurement of endogenous H2S levels in plasma. The first ratiometric UCL H2S nanoprobe reported here may be further developed as the next-generation diagnostic tool for the detection of inflammatory-related diseases.