RESUMEN
Shortwave infrared (SWIR) light emitters and detectors are crucial in numerous applications. Conventionally, SWIR devices rely on epitaxially grown narrow bandgap semiconductors, such as InGaAs, which are expensive to fabricate and difficult to integrate with silicon complementary metal-oxide-semiconductors (CMOS). Colloidal quantum dots (CQDs) have emerged as low-cost alternatives to epitaxially grown semiconductors, offering integration with CMOS through solution-processing methods. However, the predominant SWIR-active CQD systems rely on heavy-metal-containing compositions (PbS and HgTe), hindering the adoption of CQD SWIR technology. InAs CQDs are promising substitutes in SWIR applications. However, synthesizing SWIR-active InAs CQDs is challenging, often constraining them to the visible or near-infrared regions. To achieve SWIR bandgaps, large InAs CQDs are typically required; such CQDs are prone to having surface traps that quench photogenerated charge carriers, adversely affecting device performance. Here, we report a two-step synthesis of surface-passivated SWIR-active InAs/ZnSe core/shell colloidal nanorod quantum dots (CNQDs). These surface-passivated CNQDs are highly emissive and tunable over the entire technologically important region (1200-1800 nm) of the SWIR window with photoluminescence quantum yields as high as 60%. Using these SWIR-active InAs/ZnSe CNQDs, we demonstrated an SWIR-active InAs CQD photodetector, achieving a record high external quantum efficiency of â¼15% at â¼1450 nm and a low dark current of â¼10-2 mA/cm2.
RESUMEN
Colloidal quantum dots (CQDs) are emerging materials for short-wave infrared (SWIR, ≈1100-3000 nm) photodetectors, which are technologically important for a broad array of applications. Unfortunately, the most developed SWIR CQD systems are Pb and Hg chalcogenides; their toxicity and regulated compositions limit their applications. InSb CQD system is a potential environmentally friendly alternative, whose bandgap in theory, is tunable via quantum confinement across the SWIR spectrum. However, InSb CQDs are difficult to exploit, due to their complex syntheses and uncommon reactive precursors, which greatly hinder their application and study. Here, a one-pot synthesis strategy is reported using commercially available precursors to synthesize-under standard colloidal synthesis conditions-high-quality, size-tunable InSb CQDs. With this strategy, the large Bohr exciton radius of InSb can be exploited for tuning the bandgap of the CQDs over a wide range of wavelengths (≈1250-1860 nm) across the SWIR region. Furthermore, by changing the surface ligands of the CQDs from oleic acid (OA) to 1-dodecanthiol (DDT), a ≈20-fold lengthening in the excited-state lifetime, efficient carrier multiplication, and slower carrier annihilation are observed. The work opens a wide range of SWIR applications to a promising class of Pb- and Hg-free CQDs.
RESUMEN
InAs colloidal quantum dots (CQDs) have emerged as candidate lead- and mercury-free solution-processed semiconductors for infrared technology due to their appropriate bulk bandgap, which can be tuned by quantum confinement, and promising charge-carrier transport properties. However, the lack of suitable arsenic precursors and readily accessible synthesis conditions have limited InAs CQDs to smaller sizes (<7 nm), with bandgaps largely restricted to <1400 nm in the near-infrared spectral window. Conventional InAs CQD synthesis requires highly reactive, hazardous arsenic precursors, which are commercially scarce, making the synthesis hard to control and study. Here, we present a controlled synthesis strategy (using only readily available and less reactive precursors) to overcome the practical wavelength limitation of InAs CQDs, achieving monodisperse InAs nanorod CQDs with bandgaps tunable from â¼1200 to â¼1800 nm, thus crossing deep into the short-wave infrared (SWIR) region. By controlling the reactivity through in situ precursor complexation, we isolate the reaction mechanism, producing InAs nanorod CQDs that display narrow excitonic features and efficient carrier multiplication. Our work enables InAs CQDs for a wider range of SWIR applications.
RESUMEN
Critical micelle concentration (cmc) is a key parameter of generally used surfactants, and many experimental techniques like tensiometry, conductivity, spectrophotometry, fluorometry, etc. for its determination have been reported. However, these contemporary methods for cmc determination are tedious, are time-consuming, are sensitive, and require sophisticated instrumentation. Herein, we demonstrate that the cmc of the surfactants can be estimated via monitoring the variation in the apparent weight of a density bottle floating in a surfactant solution as a function of surfactant concentration. The proposed method requires the use of a simple weighing balance; a cost-affordable instrument always available in scientific laboratories. The proposed method is simple to execute and does not require any complicated data analysis procedures. As an experimental proof attached to the claim, we demonstrate the estimation of the cmcs of all types of surfactants, viz., anionic, cationic, and nonionic, through the formulated method. The results obtained in terms of cmc values of the chosen surfactants closely match those reported through the use of different standardized protocols. The formulated experimental protocol is desirable in terms of the simplicity of the protocol, accuracy, and reproducibility of the results, and cost and accessibility of the required instrument. All these attributes of the presented protocol qualify it as an appropriate substitute to the modern techniques commonly used for the cmc determination.