We experimentally demonstrate the direct-to-indirect bandgap transition of monolayer MoS2 under hydrostatic pressure.

Engineering the substrate of 2D transition metal dichalcogenides can couple the quasiparticle interaction between the 2D material and substrate, providing an additional route to realize conceptual quantum phenomena and novel device functionalities, such as realization of a 12-time increased valley spitting in single-layer WSe through the interfacial magnetic exchange field from a ferromagnetic EuS substrate, and band-to-band tunnel field-effect transistors with a subthreshold swing below 60 mV dec at room temperature based on bilayer n-MoS and heavily doped p-germanium, etc. Here, it is demonstrated that epitaxially grown single-layer MoS on a lattice-matched GaN substrate, possessing a type-I band alignment, exhibits strong substrate-induced interactions. The phonons in GaN quickly dissipate the energy of photogenerated carriers through electron-phonon interaction, resulting in a short exciton lifetime in the MoS /GaN heterostructure. This interaction enables an enhanced valley helicity at room temperature (0.33 ± 0.05) observed in both steady-state and time-resolved circularly polarized photoluminescence measurements. The findings highlight the importance of substrate engineering for modulating the intrinsic valley carriers in ultrathin 2D materials and potentially open new paths for valleytronics and valley-optoelectronic device applications.

Integrating metallic halide perovskites with established modern semiconductor technology is significant for promoting the development of application-level optoelectronic devices. To realize such devices, exploring the growth dynamics and interfacial carrier dynamics of perovskites deposited on the core materials of semiconductor technology is essential. Herein, we report the incommensurate heteroepitaxy of highly oriented singlecrystal cesium lead bromide (CsPbBr 3 ) on c-wurtzite GaN/ sapphire substrates with atomically smooth surface and uniform rectangular shape by chemical vapor deposition. The CsPbBr 3 microplatelet crystal exhibits green-colored lasing under room temperature and has a structural stability comparable with that grown on van der Waals mica substrates. Time-resolved photoluminescence spectroscopy studies show that the type-II CsPbBr 3 −GaN heterojunction effectively enhances the separation and extraction of free carriers inside CsPbBr 3 . These findings provide insights into the fabrication and application-level integrated optoelectronic devices of CsPbBr 3 perovskites.

A boundary-temperature-controlled epitaxy, where the growth temperature of InN is controlled at its maximum, is used to obtain high-electronmobility InN layers on sapphire substrates by molecular beam epitaxy. The Hall-effect measurement shows a recorded electron mobility of 3280 cm 2 V À1 s À1 and a residual electron concentration of 1:47 Â 10 17 cm À3 at room temperature. The enhanced electron mobility and reduced residual electron concentration are mainly due to the reduction of threading dislocation density. The obtained Hall mobilities are in good agreement with the theoretical modelling by the ensemble Monte Carlo simulation. #

Following intensive research and development, Suntech Power has successfully commercialised its Pluto technology with 0.5 GW annual production capacity, delivering up to 10% performance advantage over conventional screen-printed cells. The next generation of Pluto involves the development of improved rear surface design based on the design features of passivated emitter and rear locally diffused cells. Cells with an average efficiency over 20% were fabricated on 155 cm 2 commercial-grade p-type wafers using mass-manufacturing processes and equipment, with the highest single-cell efficiency independently confirmed at 20.3%. This is believed to be a record efficiency for this wafer type. Further optimisation work on contact pattern and rear surface passivation suggests the potential for further efficiency increase approaching 23%.

Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.

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Dirac-like surface states on surfaces of topological insulators have a chiral spin structure with spin locked to momentum, which is interesting in physics and may also have important applications in spintronics. In this work, by measuring the tunable helicity-dependent photocurrent (HDP), we present an identification of the HDP from the Dirac-like surface states at room temperature. It turns out that the total HDP has two components, one from the Dirac-like surface states, and the other from the surface accumulation layer. These two components have opposite directions. The clear gate tuning of the electron density as well as the HDP signal indicates that the surface band bending and resulted surface accumulation are successfully modulated by the applied ionic liquid gate, which provides a promising way to the study of the Dirac-like surface states and also potential applications in spintronic devices.