A Unique Blend of 2-Fluorenyl-2-anthracene and 2-Anthryl-2-anthracence Showing White Emission and High Charge Mobility.

White-light-emitting materials with high mobility are necessary for organic white-light-emitting transistors, which can be used for self-driven OLED displays or OLED lighting. In this study, we combined two materials with similar structures-2-fluorenyl-2-anthracene (FlAnt) with blue emission and 2-anthryl-2-anthracence (2A) with greenish-yellow emission-to fabricate OLED devices, which showed unusual solid-state white-light emission with the CIE coordinates (0.33, 0.34) at 10 V. The similar crystal structures ensured that the OTFTs based on mixed FlAnt and 2A showed high mobility of 1.56 cm2 V-1 s-1 . This simple method provides new insight into the design of high-performance white-emitting transistor materials and structures.

A Redox-Dependent Electrochromic Material: Tetri-EDOT Substituted Thieno[3,2-b]thiophene.

Organic electrochromic materials change color rapidly under applied potential. A butterfly-shaped compound, 5,5',-5″,-5'″-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl) tetrakis-(2,3-dihydrothieno[3,4-b][1,4]dioxine) (t-EDOT-TT) is synthesized for the first time and polymerized at different potentials via electropolymerization technique. By applying different polymerization potentials, the optical and electrochromic properties of this newly synthesized polymer can be tuned. Owing to the dependence of functional group position in the polymer structure on the redox potential, this polymer can be utilized in very interesting organic optoelectronic applications.

Polar-Electrode-Bridged Electroluminescent Displays: 2D Sensors Remotely Communicating Optically.

A novel geometry for electroluminescent devices, which does not require transparent electrodes for electrical input, is demonstrated, theoretically analyzed, and experimentally characterized. Instead of emitting light through a conventional electrode, light emission occurs through a polar liquid or solid and input electrical electrodes are coplanar, rather than stacked in a sandwich configuration. This new device concept is scalable and easily deployed for a range of modular alternating-current-powered electroluminescent light sources and light-emitting sensing devices. The polar-electrode-bridged electroluminescent displays can be used as remotely readable, spatially responsive sensors that emit light in response to the accumulation and distribution of materials on the device surface. Using this device structure, various types of alternating current devices are demonstrated. These include an umbrella that automatically lights up when it rains, a display that emits light from regions touched by human fingers (or painted upon using a mixture of oil and water), and a sensor that lights up differently in different areas to indicate the presence of water and its freezing. This study extends the dual-stack, coplanar-electrode device geometry to provide displays that emit light from a figure drawn on an electroluminescent panel using a graphite pencil.

An unusual photoconductive property of polyiodide and enhancement by catenating with 3-thiophenemethylamine salt.

During our investigation of perovskite solar cell materials, we serendipitously discovered an unusual photoconductive property of polyiodide, which can be enhanced greatly through the interaction of in situ-formed polyiodide and 3-thiophenemethylamine salt. This communication examined the photoconductive properties of polyiodide with and without adding different aromatic methylamine compounds. MATPI2 exhibits a high photoconductivity and short response time. The enhanced photoelectric conversion efficiencies are attributed to the strong interaction of polyiodide and the 3-thiophenemethylamine salt.

Effects of heteroatom substitution in spiro-bifluorene hole transport materials.

Three new spirofluorene-based hole transport materials, Spiro-S, Spiro-N, and Spiro-E, are synthesized by replacing the para-methoxy substituent in 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-MeOTAD) with methylsulfanyl, N,N-dimethylamino and ethyl groups. Their properties as hole transport materials in perovskite solar cells are investigated. The impact of replacing the para-methoxy substituent on bulk properties, such as the photophysical properties, HOMO/LUMO energy level, hole extraction properties and morphologies of perovskite thin films are investigated. Their optoelectronic and charge-transport properties and performance in perovskite solar cells are compared with the current benchmarked and structurally-related hole transport material (HTM) Spiro-MeOTAD. Surprisingly, the methylsulfanyl substituted spirofluorene shows the highest power conversion efficiency of 15.92% among the investigated spirofluorenes, which is an over 38% increase in PCE compared with that of Spiro-MeOTAD under similar device fabrication conditions.