Layered transition metal dichalcogenides (TMDs) have been proven to be essential building blocks for the high-performance optoelectronic devices as a result of their favorable bandgaps, extraordinary light absorption, and closed surface electronic structures. However, the in-depth exploration of their operating mechanism as insertion layers in heterojunction photodetectors is scarce. Here, we demonstrate that a Bi/Si heterojunction photodetector can achieve a superior performance by inserting a WS2 layer. A high photosensitivity of 1.4 × 108 cm2/W and an outstanding detectivity of 1.36 × 1013 cm Hz1/2 W–1 are obtained, which are comparable or even surpass those of state-of-art commercial photodetectors. The working mechanism of the Bi/WS2/Si sandwich-structured photodetector is unveiled, including the efficient passivation of the interface, enhancement of light absorption, and selective carrier blocking. Finally, a good voltage tunability of the photoresponse is also demonstrated. These findings are signi...

Promoting Photosensitivity and Detectivity of the Bi/Si Heterojunction Photodetector by Inserting a WS2 Layer.

First-Principles Calculations to Investigate the Refractive Index and Optical Dielectric Constant of Na 3 Sb X 4 ( X = S, Se) Ternary Chalcogenides

Using the many-body perturbation GW theory, we study the quasiparticle conduction-band offsets of phosphorene, a two-dimensional atomic layer of black phosphorus, and transition-metal dichalcogenides (TMDs). The calculated large exciton binding energies of phosphorene and TMDs indicate that their type-II heterostructures are suitable for excitonic thin-film solar cell applications. Our results show that these heterojunctions have a potential maximum power conversion efficiency of up to 12%, which can be further enhanced up to 20% by strain engineering.

Heterostructures of phosphorene and transition metal dichalcogenides for excitonic solar cells: A first-principles study

The diverse and fascinating properties of transition metal oxides stem from the strongly correlated electronic degrees of freedom; the scientific challenge and range of possible applications of these materials have caused fascination among physicists and materials scientists, thus capturing research efforts for nearly a century. Here, we focus on the binary VxOy and the ternary perovskite AVO3 and review the key aspects from the underlying physical framework and their basic properties, recent strides made in thin-film synthesis, to recent efforts to implement vanadium-based oxides for practical applications that augment existing technologies, which surpass limitations of conventional materials.

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Opportunities in vanadium-based strongly correlated electron systems

As potential photovoltaic materials, transition-metal oxides such as BiFeO3 (BFO) are capable of absorbing a substantial portion of solar light and incorporating ferroic orders into solar cells with enhanced performance. But the photovoltaic application of BFO has been hindered by low energy-conversion efficiency due to poor carrier transport and collection. In this work, a new approach of utilizing BFO as a light-absorbing sensitizer is developed to interface with charge-transporting TiO2 nanoparticles. This mesoporous all-oxide architecture, similar to that of dye-sensitized solar cells, can effectively facilitate the extraction of photocarriers. Under the standard AM1.5 (100 mW cm-2 ) irradiation, the optimized cell shows an open-circuit voltage of 0.67 V, which can be enhanced to 1.0 V by tailoring the bias history. A fill factor of 55% is achieved, which is much higher than those in previous reports on BFO-based photovoltaic devices. The results provide here a new viable approach toward developing highly tunable and stable photovoltaic devices based on ferroelectric transition-metal oxides.

Ferroelectric BiFeO3 as an Oxide Dye in Highly Tunable Mesoporous All-Oxide Photovoltaic Heterojunctions.

Finding solar absorbers that are chemically stable and made of abundant elements will promote the improvement of photovoltaic technology. Perhaps surprisingly, the prototypical Mott insulator LaVO${}_{3}$ is promising in this arena, as it strongly absorbs visible light and has a suitable band gap. The authors study the optical and transport properties of this material in a working device, discussing the advantages and challenges of using a Mott insulator, and showing the way for further solar cells based on strongly correlated electron systems.

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Kaidi Yuan

Papers

Device Performance of the Mott Insulator LaVO 3 as a Photovoltaic Material