The design and characterization of metal-organic complexes for optoelectronic applications is an active area of research. The metal-organic complex offers unique optical and electronic properties arising from the interplay between the inorganic metal and the organic ligand. The ability to modify chemical structure through control over metal-ligand interaction on a molecular level could directly impact the properties of the complex. When deposited in thin film form, this class of materials enable the fabrication of a wide variety of low-cost electronic and optoelectronic devices. These include light emitting diodes, solar cells, photodetectors, field-effect transistors as well as chemical and biological sensors. Here we present an overview of recent development in metal-organic complexes with controlled molecular structures and tunable properties. Advances in extending the control of molecular structures to solid materials for energy conversion and information technology applications will be highlighted.

Printed electronics are an important enabling technology for the development of low-cost, large-area, and flexible optoelectronic devices. Transparent conductive films (TCFs) made from solution-processable transparent conductive materials, such as metal nanoparticles/nanowires, carbon nanotubes, graphene, and conductive polymers, can simultaneously exhibit high mechanical flexibility, low cost, and better photoelectric properties compared to the commonly used sputtered indium-tin-oxide-based TCFs, and are thus receiving great attention. This Review summarizes recent advances of large-area flexible TCFs enabled by several roll-to-roll-compatible printed techniques including inkjet printing, screen printing, offset printing, and gravure printing using the emerging transparent conductive materials. The preparation of TCFs including ink formulation, substrate treatment, patterning, and postprocessing, and their potential applications in solar cells, organic light-emitting diodes, and touch panels are discussed in detail. The rational combination of a variety of printed techniques with emerging transparent conductive materials is believed to extend the opportunities for the development of printed electronics within the realm of flexible electronics and beyond.

Paper-based supercapacitors (SCs), a novel and interesting group of flexible energy storage devices, are attracting more and more attention from both industry and academia. Cellulose papers with a unique porous bulk structure and rough and absorptive surface properties enable the construction of paper-based SCs with a reasonably good performance at a low price. The inexpensive and environmentally friendly nature of paper as well as simple fabrication techniques make paper-based SCs promising candidates for the future 'green' and 'once-use-and-throw-away' electronics. This review introduces the design, fabrication and applications of paper-based SCs, giving a comprehensive coverage of this interesting field. Challenges and future perspectives are also discussed.

Flexible and stretchable electronics represent today's cutting-edge electronic technologies. As the most-fundamental component of electronics, the thin-film electrode remains the research frontier due to its key role in the successful development of flexible and stretchable electronic devices. Stretchability, however, is generally more challenging to achieve than flexibility. Stretchable electronic devices demand, above all else, that the thin-film electrodes have the capacity to absorb a large level of strain (>>1%) without obvious changes in their electrical performance. This article reviews the progress in strategies for obtaining highly stretchable thin-film electrodes. Applications of stretchable thin-film electrodes fabricated via these strategies are described. Some perspectives and challenges in this field are also put forward.

This review summarizes how printing methods can revolutionize the manufacturing of supercapacitors – promising energy storage devices for flexible electronics.

This review introduces the design, opportunities, and challenges of organic gain media for organic solid-state lasers, especially for organic semiconductor lasers, providing a clear panorama for this interesting and exciting research field.

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Luminescence from organic materials is of long-standing and continuing interest, not only from a fundamental scientific perspective, but also for its promising technological relevance in applications such as organic light-emitting diodes (OLEDs) [1,2] and lasers. [3][4][5] So far, the most widely pursued materials have been either small molecules/oligomers or fully-fledged polymers, with fewer examples of efficient intermediate-molecular-weight luminescent materials. Here, we establish a novel series of nanosized monodisperse starburst macromolecules as valuable platforms for investigating the impact of molecular structure on condensed-phase optical and optoelectronic properties. Our results show that long fluorene chain lengths are not a necessary prerequisite for highly efficient solid-state luminescence. Indeed, for the investigated materials, arm lengths of just two or three fluorene units are found to be appropriate. Pure and stable deep-blue electroluminescence (EL) and ultralow-threshold lasing have been achieved, demonstrating that this class of materials is of substantial interest for a variety of luminescence applications.One of the key goals for the organic electronics industry is the development of manufacturable organic luminescent materials that can emit efficiently in the condensed state, since commercial applications in OLEDs and lasers are predicated on the ability to construct solid-state devices at low cost, in which the active materials are not subject to efficient nonradiative excited-state decay. Unfortunately, whilst many previously studied conjugated molecules with a planar and rigid structure emit strongly in dilute solution, they become only weakly luminescent in the solid-state, due to the formation of (physical) dimers and aggregates that quench singlet luminescence and/or facilitate the formation of excimer states, which often possess relatively low emission efficiencies. [6,7] These quenching effects can be the consequence of intrinsic molecular properties or may simply be the result of inadvertent degradation during synthesis, processing, device operation, or the presence of impurities. For example, the formation of C --O bonds via oxidative degradation is a common problem for conjugated polymers, [8] and has been identified as the cause of luminescence quenching for a number of materials. Extensive studies on linear polyfluorenes [9][10][11][12] have shown that they can suffer severely from the effects of oxidation (leading to the formation of fluorenone moieties within the polymer backbone). The result is a general quenching of emission efficiency, and the appearance of a green emission band that leads to a loss of the desirably saturated blue emission color (a particularly attractive attribute of polyfluorenes for display applications). There is still much debate on the origin of the green band, [11,12] but we strongly favor the fluorenone-fluorenone excimer explanation.