We demonstrate extraordinary photoconductive behavior in two-dimensional (2D) crystalline indium selenide (In2Se3) nanosheets. Photocurrent measurements reveal that semiconducting In2Se3 nanosheets have an extremely high response to visible light, exhibiting a photoresponsivity of 3.95 × 10(2) A·W(-1) at 300 nm with an external quantum efficiency greater than 1.63 × 10(5) % at 5 V bias. The key figures-of-merit exceed that of graphene and other 2D material-based photodetectors reported to date. In addition, the photodetector has a fast response time of 1.8 × 10(-2) s and a specific detectivity of 2.26 × 10(12) Jones. The photoconductive response of α-In2Se3 nanosheets extends into ultraviolet, visible, and near-infrared spectral regions. The high photocurrent response is attributed to the direct band gap (EG = 1.3 eV) of In2Se3 combined with a large surface-area-to-volume ratio and a self-terminated/native-oxide-free surface, which help to reduce carrier recombination while keeping fast response, allowing for real-time detection under very low-light conditions.

We demonstrate Schottky-barrier solar cells employing a stack of layer-structured semiconductor molybdenum disulfide (MoS(2)) nanomembranes, synthesized by the chemical-vapor-deposition method, as the critical photoactive layer. An MoS(2) nanomembrane forms a Schottky-barrier with a metal contact by the layer-transfer process onto an indium tin oxide (ITO) coated glass substrate. Two vibrational modes in MoS(2) nanomembranes, E(1)(2g) (in-plane) and A(1g) (perpendicular-to-plane), were verified by Raman spectroscopy. With a simple stacked structure of ITO-MoS(2)-Au, the fabricated solar cell demonstrates a photo-conversion efficiency of 0.7% for ~110 nm MoS(2) and 1.8% for ~220 nm MoS(2). The improvement is attributed to a substantial increase in photonic absorption. The MoS(2) nanomembrane exhibits efficient photo-absorption in the spectral region of 350-950 nm, as confirmed by the external quantum efficiency. A sizable increase in MoS(2) thickness results in only minor change in Mott-Schottky behavior, indicating that defect density is insensitive to nanomembrane thickness attributed to the dangling-bond-free layered structure.

Demonstration of hybrid bulk heterojunction (BHJ) solar photovoltaic cell employing molybdenum disulfide (MoS2)/titanium dioxide (TiO2) nanocomposite (∼15 μm thick) and poly 3-hexylthiophene (P3HT) active layers is presented in this letter. The dominant Raman peak at 146 cm−1 confirmed TiO2, while two other peaks observed at 383 cm−1 and 407 cm−1 asserted MoS2 in the nanocomposite film. The demonstrated BHJ solar cell, having a stacked structure of indium tin oxide/TiO2/MoS2/P3HT/gold, exhibits a short circuit current density of 4.7 mA/cm2, open circuit voltage of 560 mV, and photoconversion efficiency of 1.3% under standard AM1.5 illumination condition. We observe that the quality of TiO2/MoS2/P3HT interfaces, as reflected in the dark saturation current in low- and medium-forward-bias region, plays a key role in impacting solar cell performance due to interfacial recombination effect.