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.