Ligand-Length Modification in CsPbBr3 Perovskite Nanocrystals and Bilayers with PbS Quantum Dots for Improved Photodetection Performance.

Nanocrystals surface chemistry engineering offers a direct approach to tune charge carrier dynamics in nanocrystals-based photodetectors. For this purpose, we have investigated the effects of altering the surface chemistry of thin films of CsPbBr3 perovskite nanocrystals produced by the doctor blading technique, via solid state ligand-exchange using 3-mercaptopropionic acid (MPA). The electrical and electro-optical properties of photovoltaic and photoconductor devices were improved after the MPA ligand exchange, mainly because of a mobility increase up to 5 × 10-3 cm 2 / Vs . The same technology was developed to build a tandem photovoltaic device based on a bilayer of PbS quantum dots (QDs) and CsPbBr3 perovskite nanocrystals. Here, the ligand exchange was successfully carried out in a single step after the deposition of these two layers. The photodetector device showed responsivities around 40 and 20 mA/W at visible and near infrared wavelengths, respectively. This strategy can be of interest for future visible-NIR cameras, optical sensors, or receivers in photonic devices for future Internet-of-Things technology.

Developments in Colloidal Synthesis of Cu2-xS (0 ≤ x ≤ 1) Nanocrystals-An Overview.

Colloidal synthesis of Cu2-xS (x = 0 ≤ x ≤ 1) nanocrystals (NCs) has been developed in recent years as broad context and its applications for energy harvesting is widely analyzed. Exciting properties of Cu2-xS NCs such as cation exchange, localized surface plasmon resonance (LSPR) in near infra-red (NIR) region are well manipulated by altering the stoichiometry through facile colloidal method. Due to their size, shape, phase tunability and self-assembly nature, synthesis of Cu2-xS NCs through colloidal medium has many advantages. Desired phase with desired composition can be achieved through facile tuning of solvent atmosphere and physical parameters of the synthesis conditions. In this regard, the present review summarizes recent achievements made in the colloidal synthesis of Cu2-xS NCs. Their structural and phase transformation in presence of different solvents and reaction conditions have been reviewed. The crucial role of phosphine-free solvents in synthesizing various phases, morphology of Cu2-xS NCs has been discussed. Applications of these Cu2-xS NCs for solar energy harvesting in third generation solar cells have also been reviewed.

Role of Temperature and Growth Period in the Synthesis of Hydrothermally Grown TiO2 Nanorods.

Highly uniformed, surfactant free and vertically oriented titanium-di-oxide (TiO2) nanorods were grown on pre-treated fluorine doped tin oxide (FTO) using hydrothermal method through titanium tetra butoxide (Ti(OBu)4) as titanium source. Three different temperatures 130 °C, 150 °C and 180 °C were followed to grow the nanorods at a fixed reaction time of 4 h. The prepared TiO2 nanorods were annealed at the temperatures of 550 °C and 600 °C for 3 h. X-ray diffraction (XRD) analysis shows that obtained nanorods exhibit pure rutile phase. From scanning electron microscopy (SEM) analysis, it was found that increasing temperature led to decreasing the diameter of the nanorods. In addition to these, formation of hierarchical type TiO2 nanorods was also observed at 130 °C. UV-visible spectra analysis was carried out to find the influence of diameter of the nanorods on its optical properties. The plausible mechanism of the growth process is also discussed.