High-Performance Waveguide-Integrated Bi2O2Se Photodetector for Si Photonic Integrated Circuits.

Due to the excellent electrical and optical properties and their integration capability without lattice matching requirements, low-dimensional materials have received increasing attention in silicon photonic circuits. Bi2O2Se with high carrier mobility, narrow bandgap, and good air stability is very promising for high-performance near-infrared photodetectors. Here, the chemical vapor deposition method is applied to grow Bi2O2Se onto mica, and our developed polycarbonate/polydimethylsiloxane-assisted transfer method enables the clean and intact transfer of Bi2O2Se on top of a silicon waveguide. We demonstrated the Bi2O2Se/Si waveguide integrated photodetector with a small dark current of 72.9 nA, high responsivity of 3.5 A·W-1, fast rise/decay times of 22/78 ns, and low noise-equivalent power of 15.1 pW·Hz-0.5 at an applied voltage of 2 V in the O-band for transverse electric modes. Additionally, a microring resonator is designed for enhancing light-matter interaction, resulting in a wavelength-sensitive photodetector with reduced dark current (15.3 nA at 2 V) and more than a 3-fold enhancement in responsivity at the resonance wavelength, which is suitable for spectrally resolved applications. These results promote the integration of Bi2O2Se with a silicon photonic platform and are expected to accelerate the future use of integrated photodetectors in spectroscopy, sensing, and communication applications.

Catalyst-free growth of dense γ-In2Se3 nanosheet arrays and their application in photoelectric detectors.

In this work, a dense γ-In2Se3 nanosheet array has been fabricated using the chemical vapor deposition method under atmospheric pressure. Compared with crystal silicon, the photodetector based on the γ-In2Se3/p-Si heterojunction exhibits a high responsivity (96.7 mA W-1) at the near-infrared region, a presentable current on/off ratio (∼1000) and excellent detectivity (2.03 × 1012 jones). Simultaneously, the obtained photodetector demonstrated a fast response speed (0.15 ms/0.5 ms) and a broadband sensitive wavelength from ultraviolet (340 nm) to near-infrared (1020 nm). The photoelectric experimental data of the device shows that its high performance is attributed to the high-light absorption capacity of the material, the rational energy band structures of γ-In2Se3 and p-Si, and the effective separation of photo-generated carriers caused by the formed type-II heterojunction. Our work provides the primary experimental basis for the photodetection application of the γ-In2Se3 nanostructure.

Enhanced light trapping and high charge transmission capacities of novel structures for efficient photoelectrochemical water splitting.

Excellent PEC efficiency, good reusability and the super stability of trap-like SnS2/TiO2 nanotube arrays (NTs)-based photoanodes are reported. Specifically, the SnS2/TiO2-180 °C (ST-180) photoanode exhibited the highest photocurrent density (1.05 mA cm-2) and an optimal η (0.73%) at 0.5 V (vs. SCE) under simulated light irradiation (AM 1.5G), which are 4.6 and 3.8 times higher than those of pure TiO2 NTs (0.23 mA cm-2 and 0.19%). The IPCE values of ST-180 can reach 21.5% (365 nm) and 13.8% (420 nm), which are much higher than those of pure TiO2 NTs (10.6% at 365 nm and 0.8% at 420 nm). The APCE values of the pure TiO2 NTs photoelectrode are 12.8% (365 nm) and 1.1% (420 nm), while the ST-180 values are 22.3% and 14.2%, respectively. Furthermore, the generation rates of H2 and O2 for the ST-180 photoanode are 47.2 and 23.1 µmol cm-2 h-1 at 0.5 V under AM 1.5G, corresponding to faradaic efficiencies of around 80.1% and 78.3%, respectively. In short, the high-efficiency PEC water splitting performance of this SnS2/TiO2 photoanode results from the enhanced light harvesting ability of the trap-like SnS2 structure, accelerated carrier transportation properties of TiO2 NTs, and effective carrier separation of the type-II heterojunction structure. This work may offer a combinatorial strategy for the preparation of heterojunction structures with high PEC performance and can be a model structure for similar photoanode materials.