Lateral ZnO/CdS:Co heterojunction photodetectors with different doping concentrations of Co2+ show selective NIR sensitivity with a maximum detectivity of 3.1 × 1011 Jones.

Plasmon-induced hot-electron generation and its efficient transfer to the conduction band (CB) of neighboring metal oxides is an effective route to solar energy harvesting. However, until now, this process has been very inefficient due to the poor charge transfer rate from plasmonic metal nanoparticles (NPs) to the CB of the oxide semiconductor. In this work, an in situ grown synthesis method has been developed to grow plasmonic Ag NPs within a titanium oxide (TiO2) matrix. This synthesis method allows us to deposit Ag NPs surrounded by a TiO2 semiconductor, which results in an efficient charge transfer from the Ag NPs to the CB of TiO2 and has been utilized for highly enhanced electro-photocatalytic H2 generation. Photoelectrochemical measurement of optimized Ag­(NPs)-TiO2 thin film photoanodes showed a high photocurrent generation at a density of 42 mA cm–2 in 1 M KOH solution, which is three orders of magnitude higher than that of pure TiO2, and stability for more than 1.5 h. These data indicates that it has excellent potential application for photoelectrochemical (PEC) water splitting. An intense photocurrent generation in the region of plasmonic absorption of Ag NPs with a peak position of 435 nm has been observed; this photocurrent generation reveals direct evidence of a strong contribution of plasmon-induced hot electrons for solar energy conversion.

No abstract

A heavy-metal-free chalcopyrite (CuFeS 2 ) nanocrystal has been synthesized via microwave-assisted growth. Large-scale nanocrystals with an average particle size of 5 nm are fabricated by this technique within a very short period of time without any need for organic ligands. Scanning electron microscopy study (SEM) of individual synthesis steps indicates that aggregates of nanocrystals are formed as flakes during microwave-assisted synthesis. The colloidal solution of the CuFeS 2 nanocrystal was prepared by sonicating these flakes. Transmission electron microscopy (TEM) study reveals the growth of sub-10 nm CuFeS 2 nanocrystals that are further characterized by X-ray diffraction. UV–visible absorption spectroscopic study shows that the band gap of this nanocrystal is ∼1.3 eV. To investigate the photosensitive nature of this nanocrystal, a bilayer p–n heterojunction photodetector has been fabricated using this nontoxic CuFeS 2 nanocrystal as a photoactive material and n-type ZnO as a charge-transport layer. The detectivity of this photodetector reaches above 10 12 Jones in visible and near-infrared (NIR) regions under 10 V external bias, which is significantly high for a nontoxic nanocrystal-based photodetector.

A rapid microwave-polyol technique is developed to grow bare-surface sub-10-nm lead sulfide (PbS) colloidal nanocrystals (NCs) of uniform size. Growth involves three distinct dynamical stages. PbS NCs homogeneously nucleate and undergo a fast growth process that spontaneously aggregates them into a continuous microstructure of PbS. Next, the interaction of low-power microwave irradiation with the NCs' dipole moments along different crystallographic axes leads to the development of strain at the NCs' grain boundaries, which ultimately causes dissociation of the aggregated microstructures into individual uniform-sized PbS NCs. The most distinctive feature of this growth technique is the bare nature and uniform size of the NCs produced. This gives the freedom to fabricate a highly packed NC thin film, which is essential for enhanced charge-transport properties. It simultaneously also precludes the need of undergoing a detrimental solid-state ligandexchange process, which is indispensably required for casting thin films from conventional counterpart long-aliphatic-ligand-capped NCs. To realize the photosensitivity and charge-transport nature of these microwave-synthesized NCs, we fabricated a lateral heterojunction photoconductor and a phototransistor that work on the principal of electron transfer to the metal oxide layer. The photoconductor exhibits prominent multispectral photosensitivity in the visible region, demonstrating high external quantum efficiency and detectivity of 7.42 × 10 2 % and 1.07 × 10 11 jones, respectively. Further, it also shows superior photocurrent generation with respect to the conventional hot-injection-method-synthesized PbS NC-based photoconductor, indicating more efficient inter-NC charge transport in its NC thin film. The unencapsulated photoconductor exhibits a long air-storage lifetime, which reflects air stability of the device and PbS NCs. In addition to the photoconductor, the metal oxide/PbS heterojunction phototransistor also shows superior photosensitivity with a responsivity and a response time of 3 × 10 −2 A/W and 2.2 s, respectively.