A notable exception is Bi 2 Te 3 [ 2,3 ] and compounds based on it that have comparatively high hexagonal symmetry. This severely restricts the exploration of TE materials to a small percentage of semiconductors that possess high-symmetry cubic structures, and thus excludes a large number of low-symmetry non-cubic materials even though they might manifest ideal bandgaps and low thermal conductivities. Directly determined by the chemical nature of its constituents, the crystal structure of a given material is rigid and rarely can be turned from low symmetry to high symmetry short of external stimuli such as pressure. It remains a key challenge to discover or design novel high-performance TE compounds among non-cubic materials. In this work, taking a hint from the recently emerging chalcopyrite TE materials with reasonable zT values, [14][15][16][17][18][19][20][21][22] we report on our successful approach of rationally tuning crystal structures to design pseudocubic or cubic-like structure blocks in non-cubic materials that lead directly to cubic-like degenerate band-edge electronic states and thus high power factors and enhanced zT values in a few carefully selected chalcopyrites (see Figure 1 ).The pseudocubic structure approach is here understood as a realization of cubic-like, highly degenerate electronic bands at band edges of non-cubic materials through a complex architecture containing an inherently long-range, nearly cubic framework as well as localized short-range non-cubic lattice distortions (see Figure 1 b). Electronic transport processes are dominated by the long-range cubic framework displaying cubic-like highly degenerate band edges and prospects for multi-valley carrier pockets, while the heat conduction is blocked by the presence of large, locally non-cubic lattice distortions. Thus, a very special character of the pseudocubic structure allows the design of high-performance novel TE materials with the ability to simultaneously optimize electrical and thermal transport properties. Binary zinc blende materials have a typical cubic structure with degenerate electron band edges (see Figure 1 a). Starting from non-cubic tetragonal chalcopyrites, the cation sublattice can be tuned to show cubic or nearly cubic framework, while the anion sublattice shows a locally distorted non-cubic framework with two types of irregular tetrahedra in ternary chalcopyrites, leading to a periodic supercell with a cubic framework (Figure 1 b). The high symmetry cubic supercell results in cubic-like degenerate electron bands at the gamma point of the folded Brillouin zone in tetragonal chalcopyrites, representing an ideal pseudocubic structure (see Figure 1 b). Furthermore, through a rationally designed mixing strategy, the emerging complex solid solution chalcopyrites might show an increased randomness of the locally irregular tetrahedra while maintaining the cubic-like Energy harvesting requires clean and highly effi cient energyconversion technologies. Thermoelectricity (TE) is one such technology that achieves thermal-t...

PEALD deposition was used to reduce the effective deposition temperature of SnO2 electron selective layers without compromising the performance of perovskite solar cells.

CuIn1−xCdxTe2 materials (x = 0, 0.02, 0.05, and 0.1) are prepared using melting-annealing method and the highly densified bulk samples are obtained through Spark Plasma Sintering. The X-ray diffraction data confirm that nearly pure chalcopyrite structures are obtained in all the samples. Due to the substitution of Cd at In sites, the carrier concentration is greatly increased, leading to much enhanced electrical conductivity and power factor. The single parabolic band model is used to describe the electrical transport properties of CuInTe2 and the low temperature Hall mobility is also modeled. By combing theoretical model and experiment data, the optimum carrier concentration in CuInTe2 is proposed to explain the greatly enhanced power factors in the Cd doped CuInTe2. In addition, the thermal conductivity is reduced by extra phonon scattering due to the atomic mass and radius fluctuations between Cd and In atoms. The maximum zTs are observed in CuIn0.98Cd0.02Te2 and CuIn0.9Cd0.1Te2 samples, which are improved by over 100% at room temperature and around 20% at 600 K.

Within the past few years, the record efficiency of inorganic–organic perovskite solar cell (PSC) has improved rapidly up to over 20%. However, the viability of commercialization of the PSC technology has been seriously questioned due to the moisture‐ and thermal‐induced instabilities. Here, it is demonstrated that these issues may be mitigated via cell structure design and contact engineering. By employing the hole‐conductor layer‐free cell structure and a bi‐layer back contact consisting of a carbon/CH3NH3I composite layer and a compact hydrophobic carbon layer, the PSCs have shown excellent stability, inhibiting moisture ingression and heat‐induced perovskite degradation. It is found that, the unique bi‐layer contact enables the optimization of perovskite absorbers during thermal stress. As a result, instead of degradation, the devices present enhanced performance under heating at 100 °C for 30 min. The best‐performing cell shows a final efficiency of 13.6% from an initial efficiency of 11.3% after thermal stress. Upon encapsulation, these cells can even retain 90% of the initial efficiencies after water exposure and over 100% initial efficiency under thermal stress at 150 °C for half an hour. This approach provides a facile way for stabilizing the PSCs and opens a door for viable commercialization of the emerging PSC technology.

Polycrystalline samples of the title thermoelectric solid solution of title (x = 0—0.5, δ = 0.02—0.05) are prepared by melting and annealing stoichiometric amounts of the elements (graphite crucible in evacuated silica tubes, 1.

The properties of nanomaterials are highly dependent on their size, shape and composition. Compared with zero-dimensional nanoparticles, the increased dimension of a one-dimensional silver nanowire (AgNW/Ag NW) leads to extra challenges on synthesizing it with controllable sizes. Here, a convenient way for the synthesis of AgNWs with tunable sizes has been developed simply by adjusting the amount of salt additives, i.e., ferric chloride (FeCl), or Fe(NO) & KCl. The average diameter and length of nanowires are readily tailored within 45-220 nm and 10-230 μm, respectively. The distinctive roles of Fe and Cl played during the growth stages of Ag NWs were revealed by comparative experiments and a heterogeneous nucleation model with the assistance of oxidative etching was proposed to elucidate the growth mechanism. Afterwards, transformations in XRD patterns from nanometer-size effects and quantitative relation for size-dependent peak wavelength of surface plasmon resonances (SPRs) in UV-vis spectroscopy of these nanowires were studied. In addition, as transparent conductive materials (TCMs), these metal nanowires were utilized to fabricate transparent conductive films (TCFs), and the effects of their diameters and lengths were elucidated. Very/ultra-long nanowires with a high aspect ratio up to 1600 achieved impressive properties of R = 12.4 ohm sq at T% = 90.1% without any post treatment. This facile method for the size-tunable growth of uniform AgNWs with high yield is attractive and ready to be home-made, which is believed to promote research in their potential applications, especially in optoelectronic devices and flexible electronics.

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A series of small molecule HTMs with two-dimensional and three-dimensional cores is simulated and the results show that the three-dimensional cores exhibit superiorities in comparison with the two-dimensional cores.