P-BiSbTe bulk materials with high texture, superior thermoelectric properties and robust mechanical performance were fabricated by laser 3D printing.

Organic-inorganic metal halide perovskite solar cells (PSCs) have been emerging as one of the most promising next generation photovoltaic technologies with a breakthrough power conversion efficiency (PCE) over 22%. However, aiming for commercialization, it still encounters challenges for the large-scale module fabrication, especially for flexible devices which have attracted intensive attention recently. Low-temperature processed high-performance electron-transporting layers (ETLs) are still difficult. Herein, we present a facile low-temperature synthesis of crystalline SnO nanocrystals (NCs) as efficient ETLs for flexible PSCs including modules. Through thermal and UV-ozone treatments of the SnO ETLs, the electron transporting resistance of the ETLs and the charge recombination at the interface of ETL/perovskite were decreased. Thus, the hysteresis-free highly efficient rigid and flexible PSCs were obtained with PCEs of 19.20 and 16.47%, respectively. Finally, a 5 × 5 cm flexible PSC module with a PCE of 12.31% (12.22% for forward scan and 12.40% for reverse scan) was fabricated with the optimized perovskite/ETL interface. Thus, employing presynthesized SnO NCs to fabricate ETLs has showed promising for future manufacturing.

Interactions among various film growth parameters, such as the substrate temperature (Tsub), film thickness (d), and composition, play a crucial role in controlling the type and density of the intrinsic point defects. In turn, the point defects modulate and control electronic transport properties of Bi2Te3 films. We have grown n-type Bi2Te3 films with different d by molecular beam epitaxy at different Tsub. The formation of point defects was analyzed by a combined use of angle-resolved photoelectron spectroscopy (ARPES) and electronic transport measurements. Two important findings were made: (i) the negatively charged vacancies, VTe··, initially the dominant intrinsic defects, transform gradually during the growth process into positively charged anti-site defects, BiTe′, driven by thermal annealing from a continuously heated substrate; and (ii) from the film's surface into the inner strata of the film, the density of VTe·· decreases while the density of BiTe′ increases, leading to a gradient of vacancies and anti-site defects along the film growth direction. As a result, the electron density in Bi2Te3 films decreases monotonically with increasing d. Moreover, elevating Tsub leads to a more significant in situ annealing effect and an eventual onset of intrinsic excitations that deteriorates electronic transport properties. The thinnest Bi2Te3 film (16 nm) grown at Tsub = 245 °C has the highest electron concentration of 2.03 × 1020 cm−3 and also the maximum room temperature power factor of 1.6 mW m−1 K−2 of all grown epitaxial films. The new insights regarding the defect formation and transformation pave the way for further optimization of electronic transport properties of n-type Bi2Te3-based films.

Miniaturization of efficient thermoelectric (TE) devices has long been hindered by the weak mechanical strength and insufficient heat-to-electricity conversion efficiency of zone-melted (ZM) ingots. Here, we successfully prepared a robust high-performance p-type Bi 0.4 Sb 1.6 Te 3.72 bulk alloy by combining an ultrafast thermal explosion reaction with the spark plasma sintering (TER-SPS) process. It is observed that the introduced excess Te not only enhances the (00l)-oriented texture to ensure an outstanding power factor (PF) of 5 mW m −1 K −2 , but also induces extremely high-density line defects of up to 10 11 -10 12 cm −2. Benefiting from such heavily dense line defects, the enhancement of the electronic thermal conductance from the increased electron mobility is fully compensated by the stronger phonon scattering, leading to an evident net reduction in total thermal conductivity. As a result, a superior ZT value of~1.4 at 350 K is achieved, which is 40% higher than that of commercial ZM ingots. Moreover, owing to the strengthening of grain refinement and highdensity line defects, the mechanical compressive stress reaches up to 94 MPa, which is 154% more than that of commercial single crystals. This research presents an effective strategy for the collaborative optimization of the texture, TE performance, and mechanical strength of Bi 2 Te 3 -based materials. As such, the present study contributes significantly to the future commercial development of miniature TE devices.

Developing suitable catalysts capable of receiving injected electrons and possessing active sites for hydrogen evolution reaction (HER) is the key to building an efficient dyesensitized system for hydrogen production. Fe 3 S 4 is generally regarded as an inferior HER catalyst among the metal sulfide family, mainly due to its weak surface adsorption toward H atoms. In this work, we demonstrate a facile metal−organic frameworkderived method to synthesize uniform Fe 3 S 4 nanorods and active them for HER by Ni doping. Our experimental results and theoretical calculations reveal that Ni doping can greatly modify the electronic structure of Fe 3 S 4 nanorods, improving their electron conductivity and optimizing their surface adsorption energy toward H atoms. Sensitized by a commercial organic dye (eosin-Y), 1%Ni-doped Fe 3 S 4 nanorods display a high H 2 production rate of 3240 μmol g cat −1 h −1 with an apparent quantum yield of 12% under 500 nm wavelength, which is significantly higher than that of pristine Fe 3 S 4 and even higher than that of 1% Pt-deposited Fe 3 S 4 . The working mechanism of this dye-sensitized system is explored, and the effect of Ni-doping concentration has been studied. This work presents a facile strategy to synthesize metal-doped sulfide nanocatalysts with greatly enhanced activity toward photocatalytic H 2 production.