To support the ever-growing demand for faster, energy-efficient computation, more aggressive scaling of the transistor is required. Two-dimensional (2D) transition metal dichalcogenides (TMDs), with their ultra-thin body, excellent electrostatic gate control, and absence of surface dangling bonds, allow for extreme scaling of the channel region without compromising the mobility. New device geometries, such as stacked nanosheets with multiple parallel channels for carrier flow, can facilitate higher drive currents to enable ultra-fast switches, and TMDs are an ideal candidate for that type of next generation front-end-of-line field effect transistor (FET). TMDs are also promising for monolithic 3D (M3D) integrated back-end-of-line FETs due to their ability to be grown at low temperature and with less regard to lattice matching through van der Waals (vdW) epitaxy. To achieve TMD FETs with superior performance, two important challenges must be addressed: (1) complementary n- and p-type FETs with small and reliable threshold voltages are required for the reduction of dynamic and static power consumption per logic operation, and (2) contact resistance must be reduced significantly. We present here the underlying strengths and weaknesses of the wide variety of methods under investigation to provide scalable, stable, and controllable doping. It is our Perspective that of all the available doping methods, substitutional doping offers the ultimate solution for TMD-based transistors.

Near-perfect light absorbers (NPLAs), with absorbance, $${{{{{{{\mathcal{A}}}}}}}}$$A , of at least 99%, have a wide range of applications ranging from energy and sensing devices to stealth technologies and secure communications. Previous work on NPLAs has mainly relied upon plasmonic structures or patterned metasurfaces, which require complex nanolithography, limiting their practical applications, particularly for large-area platforms. Here, we use the exceptional band nesting effect in TMDs, combined with a Salisbury screen geometry, to demonstrate NPLAs using only two or three uniform atomic layers of transition metal dichalcogenides (TMDs). The key innovation in our design, verified using theoretical calculations, is to stack monolayer TMDs in such a way as to minimize their interlayer coupling, thus preserving their strong band nesting properties. We experimentally demonstrate two feasible routes to controlling the interlayer coupling: twisted TMD bi-layers and TMD/buffer layer/TMD tri-layer heterostructures. Using these approaches, we demonstrate room-temperature values of $${{{{{{{\mathcal{A}}}}}}}}$$A =95% at λ=2.8 eV with theoretically predicted values as high as 99%. Moreover, the chemical variety of TMDs allows us to design NPLAs covering the entire visible range, paving the way for efficient atomically-thin optoelectronics.

Polycrystalline silicon on oxide (POLO) junction passivating contacts have recently been demonstrated as carrier selective contacts for high-efficiency silicon solar cells. The carrier transport through these contacts has been attributed to two competing mechanisms: 1) carrier tunneling through ultrathin oxide and 2) transport through weak spots (pinholes) - the nanoscale regions where oxide thickness has been completely or partially compromised during the processing. In this paper, we use two dimensional device simulations to compare the relative effects of these mechanisms on solar cell characteristics with n-type POLO contact. We show that variation in pinhole areal density (Dph) or the tunnel oxide thickness (tox) both result in qualitatively similar trends in the cell characteristics under dark and light. For a given tox, an exponential variation in results in trends that are similar to those for a linear variation in tox. The effect of pinholes on contact resistance (ρc) and saturation current density (Jo) is most significant for relatively thicker oxides (≥ 2 nm). For tox ≤ 1 nm, ρc and Jo become essentially insensitive to pinholes for Dph < 10¹⁰ cm⁻². The modeling results are compared with a set of published experimental data to predict the possible roles of various mechanisms.

In two-dimensional (2D) materials research, exfoliating 2D transition metal dichalcogenides (TMDs) from their growth substrates for device fabrication remains a significant challenge. Current methods, such as those involving polymers, metals, or chemical etchants, suffer from limitations like contamination, defect introduction, and a lack of scalability. Here, we demonstrate a selenium capping-based exfoliation technique. Its advantage lies in its ability to enable the clean, contamination-free exfoliation and transfer of TMD films. We successfully exfoliated and transferred monolayer and multilayer TMD films, including WSe₂ and MoSe₂. The selenium capping layer not only enables seamless exfoliation but also protects the film from oxidation, as confirmed by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach is versatile and applicable to a range of TMDs and thicknesses, paving the way for the high-quality, scalable integration of 2D materials into nanoelectronic devices.

Agrivoltaics is an innovative approach in which solar photovoltaic (PV) energy generation is collocated with agricultural production to enable food-energy-water synergies and landscape ecological conservation. This dual-use requirement leads to unique co-optimization challenges (e.g. shading, soiling, spacing) that make module technology and farm topology choices distinctly different from traditional solar farms. Here we compare the performance of the traditional optimally-titled North/South (N/S) faced monofacial farms with a potential alternative based on vertical East/West (E/W)-faced bifacial farms. Remarkably, the vertical farm produces essentially the same energy output and photosynthetically active radiation (PAR) compared to traditional farms as long as the PV array density is reduced to half or lower relative to that for the standard ground-mounted PV farms. Our results explain the relative merits of the traditional mono facial vs. vertical bifacial farms as a function of array density, acceptable PAR-deficit, and energy production. The combined PAR/Energy yields for the vertical bifacial farm may not always be superior, it could still be an attractive choice for agrivoltaics due to its distinct advantages such as minimum land coverage, least hindrance to the farm machinery and rainfall, inherent resilience to PV soiling, easier cleaning and cost advantages due to potentially reduced elevation.