A fast and simple approach to assemble 2D and 3D gold nanoparticle-organic ligand arrays with versatile applications.

Control of morphology and chain alignment in polymer thermoelectric materials is critical to their performance. A x25 improvement in zT is reported for chain aligned films.

Hybrid lead halide perovskites have been revolutionary in the photovoltaic research field, reaching efficiencies comparable with the most established photovoltaic technologies, although they have not yet reached their competitors’ stability. The search for a stable configuration requires the engineering of the charge extraction layers; in this work, molecular doping is used as an efficient method for small molecules and polymers employed as hole transport materials in a planar heterojunction configuration on compact-TiO2. We proved the viability of this approach, obtaining significantly increased performances and reduced hysteresis on compact titania-based devices. We investigated the photovoltaic performance correlated to the hole transport material structure. We have demonstrated that the molecular doping mechanism is more reliable than oxidative doping and have verified that molecular doping in polymeric hole transport materials leads to highly efficient perovskite solar cells, with long-term stability.

N-Alkyl naphthalene diimides show a highly versatile thermally-induced polymorphic behavior, including liquid crystalline mesophases, fully characterized in powders and thin films by combining thermal, diffraction and imaging techniques.

Halide perovskites have emerged as promising candidates as the active material in photovoltaics and light-emitting diodes. They possess unusual bulk thermal transport properties that have been the focus of a number of studies, but there is much less understanding of thermal transport in thin films where a diverse range of structures and morphologies are accessible. Here, we report on the tuning of in-plane thermal conductivity in methylammonium lead iodide thin films by morphological control. Using 3-ω measurements, we find that the room temperature thermal conductivity of thermally evaporated methylammonium lead iodide perovskite films ranges from 0.31 to 0.59 W/(m K). We measure a discontinuity in thermal conductivity at the orthorhombic-tetragonal phase transition and explore this using density functional theory and attributing it to a collapse in the phonon group velocity along the c-axis of the tetragonal crystal. Moreover, we have quantified the thermal boundary resistance (Kapitza resistance) for thermally evaporated films, allowing us to estimate the Kapitza length, which is 36 ± 2 nm at room temperature and 15 ± 2 nm at 100 K. Curiously, the Kapitza resistance has a strong temperature dependence which we also explore using density functional theory, with these results suggesting an important role of methylammonium rotational modes in scattering phonons at the crystallite boundaries.

Direct photoelectrochemical response of carbon dots (CDs) was attributed to a photogenerated electron-transfer process by CDs under illumination.

The use of thermoelectric technology is attractive in many potential applications, such as energy scavenging from waste heat. The basic principles for harvesting electricity from a temperature gradient were first discovered around 180 years ago, but the contemporary technology utilizing inorganic semiconductors was only developed since the early 1950s. The widespread use of this platform has so far been limited by a combination of relatively low efficiency in energy conversion or by issues related to the utilization of rare, expensive and/or toxic elements that can be difficult to process. Much interest has been focused on the use of organic materials in thermoelectric devices, prompted by the possibility of developing large-area, low-cost devices. Research over the last 20 years has been focused on understanding and improving organic thermoelectric properties, but only recently remarkable progress published for compounds such as poly(3,4-ethylenedioxythiophene) have attracted considerable attention. This has opened the door to developing a number of organic–inorganic composites for thermoelectric applications which combine the inherently low thermal conductivity and solution processing of organic materials with the high electrical conductivity of many inorganics.