Although fullerene derivatives (e.g. PC61BM/PC71BM) are being widely used as electron acceptors in organic solar cells (OSCs), their obvious drawbacks, such as the high cost, poor absorption, limited energy levels tunability and morphological instability, have become the bottlenecks to hinder the further advancement of OSCs. Therefore, the exploration of non-fullerene electron acceptors is motivated in recent years, and the efficiencies of fullerene-free OSCs have been boosted over 13%. In this presentation, I will focus on the molecular design for highly efficient and thermally stable small molecule electron acceptors based on fused diketopyrrolopyrrole (DPP) and perylene diimide (PDI) building blocks. A new strategy of unfused-ring core is put forward to synthesize thenovel electron acceptors for OSC applications. The highly efficient and thermally stable non-fullerene organic solar cells over 11% have been fabricated by carefully designing the non-fullerene acceptors.
Transparent conductive electrodes are one of the essential components for organic optoelectronic devices, including photovoltaic cells and light-emitting diodes. Indium-tin oxide (ITO) is the most common transparent electrode in these devices due to its excellent optical and electrical properties. However, the manufacturing of ITO film requires precious raw materials and expensive processes, which limits their compatibility with mass production of large-area, low-cost devices. The optical/electrical properties of ITO are strongly dependent on the deposition processes and treatment conditions, whereas its brittleness and the potential damage to underlying films during deposition also present challenges for its use in flexible devices. Recently, several other transparent conductive materials, which have various degrees of success relative to commercial applications have been developed to address these issues. Starting from the basic properties of ITO and the effect of various ITO surface modification methods, here we review four different groups of materials, doped metal oxides, thin metals, conducting polymers, and nanomaterials (including carbon nanotubes, graphene, and metal nanowires), that have been reported as transparent electrodes in organic optoelectronic materials. Particular emphasis is given to their optical/electrical and other material properties, deposition techniques, and applications in organic optoelectronic devices.
A large number (more than 20 different kinds) of new polyacetylenes with general molecular structures of -[HC equals C(C6H4-mesogen)]p- [poly(arylacetylene) type] and -{HC equals C[(CH2)n-mesogen]}p- [poly(alkylacetylene) type] are designed and synthesized. Pendant interaction and backbone rigidity in the polymers are tuned through systematic molecular engineering endeavor, and liquid crystalline polyacetylenes (LCPAs) with novel mesomorphic, optical, and electronic properties are successfully developed. The rigid polyacetylene backbones enable ready alignments of the LCPA molecules by simple mechanical perturbations. Upon photoexcitation, the LCPAs with the poly(alkylacetylene) skeleton structure emit strong blue light clearly observable by naked eyes under normal room illumination conditions. The shape and position of the emission peaks and the color of the emitted light can be manipulated by the application of external electrical fields. The LCPAs exhibit excellent intrinsic photoconductivity in the visible spectral region in the undoped (pure) states, and doping with electron acceptor/donor further increases the photoconduction efficiency of the LCPAs.
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