P-type Polymers in Semitransparent Organic Photovoltaics.

P-type polymers are polymeric semiconducting materials that conduct holes and have extensive applications in optoelectronics such as organic photovoltaics. Taking the advantage of intrinsic discontinuous light absorption of organic semiconductors, semitransparent organic photovoltaics (STOPVs) present compelling opportunities in various potential applications such as building-integrated photovoltaics, agrivoltaics, automobiles, and wearable electronics. The characteristics of p-type polymers, including optical, electronic, and morphological properties, determine the performance of STOPVs, and the requirements for p-type polymers differ between opaque organic photovoltaics and STOPVs. Hence, in this Minireview, recent advances of p-type polymers used in STOPVs are systematically summarized, with emphasis on the effects of chemical structures, conformation structures, and aggregation structures of p-type polymers on the performance of STOPVs. Furthermore, new design concepts and guidelines are also proposed for p-type polymers to facilitate the future development of high-performance STOPVs.

Molecular Regulation of Flexible Composite Solid-Solid Phase Change Materials with Controllable Isotropic Thermal Conductivity for Thermal Energy Storage.

In recent years, graphene has been introduced into phase change materials (PCMs) to improve thermal conductivity to enhance the heat transfer efficiency in thermal energy storage. However, graphenes tend to aggregate in PCMs, leading to the low thermal conductivity efficient enhancement (TCEE), anisotropic thermal conductivity, and deterioration of mechanical performance of PCMs. In this work, we fabricated biomimetic thermally conductive solid-solid PCMs (SSPCMs) by facile blending of the graphene into well-designed polyurethane SSPCMs, in which the graphene established a controllable and highly efficient isotropic thermally conductive pathway based on the π-π stacking between the graphene and the polymer aromatic ring segment. The as-fabricated SSPCMs showed high TCEE (156.78%), excellent flexibility (328% elongation at break), high enthalpy value (>101 J/g), and solid-solid phase transition properties, under 2% loading of graphene. The proportion of in-plane to through-plane thermal conductivity can be adjusted by an elaborate design of the aromatic ring segment in polyurethane SSPCMs. We further demonstrated mechanical flexibility and photothermal property of the composites to reveal their potential in practical applications.

Achieving efficient and large-scale preparation of mesophase-nylon 11 film by random copolymerization of nylon 11 and nylon 611.

Nylon 11 is a promising functional material for future electronic devices or energy storage systems. To utilize nylon-11 in these applications, it is important to control the formation of metastable crystal phases such as the γ-phase and δ'-phase. However, controlling the formation of the applicable metastable crystal phase by the processing method is complicated and inefficient. Herein, we report a novel nylon 11-based copolymer synthesized by random copolymerization of nylon 11 and nylon 611, which can directly obtain a metastable crystal phase by simple hot-pressing. Meanwhile, high heterogeneity can stabilize the defective mesophase. Non-isothermal crystallization analysis showed that the crystallization rate decreased gradually with the increase of chemical heterogeneity in the nylon random copolymer. The resulting metastable crystal phase of the nylon copolymer is controlled by crystallization kinetics. This study clarified the mechanism of controlling the crystal structure by copolymerization of nylon 11 and nylon 611, moreover, it is promising to inspire novel nylon copolymers.