Intrinsic/doped stacked hydrogenated amorphous silicon (a-Si:H) are widely used passivation layers for amorphous/crystalline silicon (a-Si/c-Si) heterojunction solar cells. This work reports that hot wire chemical vapor deposition of doped a-Si:H can significantly modify the property of the underlying intrinsic a-Si:H (a-Si:H(i)) as well as a-Si/c-Si interface passivation, which stems from the in-diffusion of highly reactive atomic hydrogen. Fourier transform infrared spectroscopy, spectroscopic ellipsometry and Raman analyses indicate that the underlying a-Si:H(i) films become more compact and less defected as a result of network reconstruction during doped a-Si:H capping. After this reconstruction, underdense a-Si:H(i) films obtained superior passivation quality than widely used dense layers, despite the inferior quality in the initial state. Effective minority carrier lifetime of c-Si passivated by underdense a-Si:H(i) was 19.9 ms, much higher than 15.2 ms in the case of using dense a-Si:H(i). The porous structure of underdense a-Si:H(i) facilitates hydrogen diffusion towards a-Si/c-Si interface and hence a rapid reduction of interface defect densities occurs, accounting for the better passivation quality. SHJ solar cells (160 μm, 156 × 156 mm) with industry-compatible process were fabricated, yielding the efficiency up to 23.0% with high V values of 741 mV.

The fields of photovoltaics, photodetection and light emission have seen tremendous activity in recent years with the advent of hybrid organic-inorganic perovskites. Yet, there have been far fewer reports of perovskite-based field-effect transistors. The lateral and interfacial transport requirements of transistors make them particularly vulnerable to surface contamination and defects rife in polycrystalline films and bulk single crystals. Here, we demonstrate a spatially-confined inverse temperature crystallization strategy which synthesizes micrometre-thin single crystals of methylammonium lead halide perovskites MAPbX3 (X = Cl, Br, I) with sub-nanometer surface roughness and very low surface contamination. These benefit the integration of MAPbX3 crystals into ambipolar transistors and yield record, room-temperature field-effect mobility up to 4.7 and 1.5 cm2 V−1 s−1 in p and n channel devices respectively, with 104 to 105 on-off ratio and low turn-on voltages. This work paves the way for integrating hybrid perovskite crystals into printed, flexible and transparent electronics.

Lead-free hybrid perovskites have attracted immense interest as environmentally friendly light absorbers. Here, we report on tellurium (Te)-based double perovskites A2TeX6 (A = MA, FA, or BA; X = Br– or I–; MA = CH3NH3; FA = CH(NH2)2; BA = benzylamine) as potentially active materials for optoelectronic devices. These perovskites exhibit a tunable band gap (1.42–2.02 eV), a low trap density (∼1010 cm–3), and a high mobility (∼65 cm2 V–1 s–1). Encouragingly, the MA2TeBr6 single crystal with a band gap of 2.00 eV possesses a long carrier lifetime of ∼6 μs and corresponding carrier diffusion lengths of ∼38 μm, which are ideal characteristics for a material for photodetectors and tandem solar cells. Moreover, A2TeX6 perovskites are relatively robust in ambient conditions, being stable for at least two months without showing any signs of phase change. Our findings bring to the forefront a family of lead-free Te-based perovskites for nontoxic perovskite optoelectronics.

Minimizing carrier recombination losses at contact regions by using carrier-selective contact materials, instead of heavily doping the silicon, has attracted considerable attention for high-efficiency, low-cost crystalline silicon (c-Si) solar cells. Here we present a novel and stable metal nitride based hole-blocking layer for efficient silicon solar cells.The ALD-deposited tantalum nitride (TaNx) films are demonstrated to provide excellent holeblocking property on silicon surfaces, due to their small conduction band offset and large valence band offset with silicon. Thin TaNx films are found to provide not only moderate surface passivation to silicon surfaces, but also allow a relatively low contact resistivity at the TaNx n-Si heterojunctions. An efficiency over 20% is achieved on n-type silicon solar cells featuring a simple full-area electron-selective TaNx contact, representing an absolute efficiency gain of 4.0% over the control device without TaNxcontact.

The optoelectronic and photocatalytic properties of a number of semiconductor materials, including halide perovskites, have recently been found to be facet-dependent. While methylammonium lead iodide (CH3NH3PbI3) perovskite – an important material for energy applications – has shown facet-dependent electronic properties as well, most studies on CH3NH3PbI3 perovskite were performed on rhombo-dodecahedral (or rhombic) single crystals with the (200) and (112) facets exposed. In contrast, less is known about the electronic properties, including mixed conductivity behavior and possible in-plane anisotropy, of the (002) facet. Thus, we report a facile method for the growth of cuboid crystals of CH3NH3PbI3 perovskite with the (002) and (110) facets exposed. Two-terminal devices fabricated on the (002) facet demonstrate significantly improved charge transport and optoelectronic characteristics compared to those on the (200) facet of typical rhombic crystals, including: reduced ion migration, low dark current, and temporally-stable high photocurrents. These desirable characteristics of cuboid crystals are linked to their favorable growth conditions and preferred facet orientations. Our results provide a guidance for utilizing facets and crystal growth to achieve more efficient in-plane halide perovskite devices.

Conspectus Atomically precise noble metal (mainly silver and gold) nanoclusters are an emerging category of promising functional materials for future applications in energy, sensing, catalysis, and nanoelectronics. These nanoclusters are protected by ligands such as thiols, phosphines, and hydride and have sizes between those of atoms and plasmonic nanoparticles. In metallurgy, the properties of a pure metal are modified by the addition of other metals, which often offers augmented characteristics, making them more utilizable for real-life applications. In this Account, we discuss how the incorporation of various metal atoms into existing protected nanoclusters tunes their structure and properties. The process of incorporating metals into an existing cluster is known as doping; the product is known as a doped cluster, and the incorporated metal atom is called a dopant/foreign atom. We first present a brief historical overview of protected clusters and the need for doping and explain (with examples) the difference between an “alloy” and a “doped” cluster, which are two frequently confused terms. We then discuss several commonly observed challenges in the synthesis of doped clusters: (i) doping produces a mixture of compositions that prevents the growth of single crystals; (ii) doping with foreign atoms sometimes changes the overall composition and structure of the parent cluster; and (iii) doping beyond a certain number of foreign atoms decomposes the doped cluster. After delineating the challenges, we review a few potential synthetic methods for doped clusters: (i) the co-reduction method, (ii) the galvanic exchange method, (iii) ligand-induced conversion of bimetallic clusters to doped clusters, and (iv) intercluster reactions. As a foreign atom is able to occupy different positions within the structure of the parent cluster, we examine the structural relationship between the parent clusters and their different foreign-atom-doped clusters. We then show how doping enhances the stability, luminescence, and catalytic properties of clusters. The enhancement factor highly depends on the number and nature of the foreign atoms, which can also alter the charge state of the parent cluster. Atomic-level doping of foreign atoms in the parent cluster is confirmed by high-resolution electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry techniques and single-crystal X-ray diffraction methods. The photophysical properties of the doped clusters are investigated using both time-dependent and steady-state luminescence and optical absorption spectroscopies. After presenting an overview of atomic-level doping in metal clusters and demonstrating its importance for enriching the chemistry and photophysics of clusters and extending their applications, we conclude this Account with a brief perspective on the field’s future.

A novel method for the synthesis of the homogeneous homoleptic cationic tantalum(V)tetramethyl complex [(TaMe4)+ MeB(C6F5)3−] from neutral tantalumpentamethyl (TaMe5) has been described, by direct demethylation using B(C6F5)3 reagent. The aforesaid higher valent cationic tantalum complex was characterized precisely by liquid state 1H-NMR, 13C-NMR, and 1H-13C-NMR correlation spectroscopy.

Embodiments of the present disclosure describe a method of energy storage and release based on crystallization-dissolution comprising heating a solute-solvent system to decrease a solubility of a solute in the solvent and induce crystal formation; cooling a solute-solvent system to increase the solubility of the solute in the solvent and induce crystal dissolution; wherein energy is stored in the crystal upon heating and released from the crystal upon cooling.

The effect of residual Pd on hydrogen evolution activity in conjugated polymer photocatalytic systems is systematically investigated using colloidal poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) nanoparticles as a model system. Residual Pd, originating from the synthesis of F8BT via Pd catalyzed polycondensation polymerization, is observed in the form of homogeneously distributed Pd nanoparticles within the polymer. Residual Pd is essential for any hydrogen evolution to be observed from this polymer, and very low Pd concentrations (<40 ppm) are sufficient to have a significant effect on the hydrogen evolution reaction (HER) rate. The HER rate increases linearly with increasing Pd concentration from <1 ppm to approximately 100 ppm, at which point the rate begins to saturate. Transient absorption spectroscopy experiments support these conclusions, and suggest that residual Pd mediates electron transfer from the F8BT nanoparticles to protons in the aqueous medium.

An intriguing reversible band gap narrowing behavior of the lead-free hybrid perovskite single crystal DMASnI3 (DMA = CH3NH2CH3+) from yellow to black is observed without oxidation and phase transformation. We discuss the transformation mechanism in detail. More interestingly, the transformed samples in black can rapidly self-heal into yellow ones when exposed to deionized water (DI water). Contrary to other hybrid perovskites, DMASnI3 crystals exhibit excellent water phase stability. For example, DMASnI3 was immersed in DI water for 16 h and no decomposition was observed. Inspired by its excellent water phase stability, we demonstrate a potential eco-friendly application of DMASnI3 in photo-catalysis for H2 evolution in DI water. We present the first H2 evolution rate of 0.64 µmol h-1 with good recycling properties for pure DMASnI3 crystals. After the narrowing process, the optical band gap of DMASnI3 can be lowered from 2.48 eV to 1.32 eV. Systematical characterizations are applied to investigate their structures and optoelectronic properties. The reversible band gap narrowing behavior and outstanding electrical properties, such as higher carrier mobility and long carrier lifetime show that DMASnI3 has a great potential for optoelectronic applications.