Perovskites are known for their high yield photoluminescence and higher photovoltaic conversion efficiencies. To make them practically useful, the toxicity and stability issues need to be addressed. Herein, we report a less toxic and stable silver bismuth iodide quantum dot system, prepared by a modified ligand assisted reprecipitation (LARP) method. Three types of phase structures such as AgBiI 4 , Ag 2 BiI 5 , and AgBi 2 I 7 were obtained, and their structural and photophysical properties were investigated. By replacing lead (Pb), the toxicity would be reduced considerably and the optical properties persisted for more than six months at ambient conditions. The as-prepared silver bismuth iodide QDs were then used to construct photodetector devices, and the device performances were studied. The constructed photodetector devices have generated the photocurrent values of (AgBi 2 I 7 ∼ 0.12 and 0.32 mA), (Ag 2 BiI 5 ∼ 0.87 and 1.6 μA), and (AgBiI 4 ∼ 0.16 and 0.61 mA) at different biasing voltages of 0.1 and 0.2 V, respectively, under visible light irradiation. The AgBi 2 I 7 QD system generated higher photocurrent value and exhibited a better ON/OFF ratio of (I on /I off = 6.5 × 10 4 ). The silver bismuth iodide QDs based photodetectors are promising for ultraviolet photodetection.

Detection of visible blind UV radiation is not only interesting but also of technologically important. Herein, we demonstrate the efficient detection of UV radiation by using cluster like ZnS quantum dot solid nanostructures prepared by simple reflux condensation technique. The short-chain ligand 3-mercaptopropionic acid (MPA) involved in the synthesis lead to the cluster like formation of ZnS quantum dots into solids upon prolonged synthesis conditions. The ZnS QD solid formation resulted in the strong delocalization of electronic wave function between the neighboring quantum dots. It increases the photocurrent value, which can be further confirmed by the decrease in the average lifetime values from 64 to 4.6 ns upon ZnS cluster like QD solid formation from ZnS QDs. The ZnS quantum dot solid based UV sensor shows good photocurrent response and a maximum responsivity of 0.31 (A/W) at a wavelength of 390 nm, is not only competitive when compared with previous reports but also better than ZnS and metal oxide-based photodetectors. The device exhibits a high current value under low-intensity UV light source and an on/off ratio of IUV/Idark = 413 at zero biasing voltage with a fast response. Further, photocurrent device has been constructed using ZnS quantum dot solid nanostructures with graphene hybrids as an active layer to improve the enhancement of photoresponsivity.

Blue emission giving nanoscale molecular clusters of Oleylamine–Acetone system was formed by an aging assisted hydrogen bond formation between the interacting molecular systems, at room temperature. The as-formed nanoscale molecular clusters were found to be self-assembled into flower-like aggregates and shifted the emission wavelength to red colour depicting an exciton delocalization in the aggregate system. Interestingly aging process has also produced imine type binding between Oleylamine and Acetone due to the condensation reaction. The experimental conditions and formation mechanism of hydrogen bond assisted Oleylamine–Acetone molecular aggregates and imine bond assisted Oleylamine–Acetone is elaborated in this paper in a systematic experimental approach with suitable theory. Finally we have introduced this Acetone assisted aging process in In2S3 QD system prepared with Oleylamine as functional molecules. It was found that the aging process has detached Oleylamine from QD surface and as a consequence In2S3 QD embedded Oleylamine–Acetone aggregates was obtained. When this In2S3 QD embedded molecular cluster system was used as an active layer in a photo conductor device then a maximum photo current value of the order of milli Ampere was obtained. The surfactant molecules normally inhibit the charge transport between QD systems and as a result it is always problematic to have the functional molecules in the QD based transport devices. Our approach has a solution to this problem and the present paper discusses the outcome of the results in detail.