1/2/2023 0 Comments Core shell quantum dot![]() have proposed a heterojunction structure for a PbS/TiO 2-based SWIR photodetector, which can be operated either as a standalone detector or for SWIR absorption. have examined the use of PbS colloidal QD-based photodiodes, which were formed from a photosensitive PbS layer and a Schottky contact, owing to their fast response and moderate sensitivity. In a study by So et al., solution-processed inorganic SWIR photodetectors were fabricated using large, highly monodispersed PbS QDs to provide good light-sensitivity, stability, and device lifetime. Nevertheless, an attractive platform for low-cost photodetectors in the SWIR spectral region is provided by lead sulfide (PbS) QDs owing to their excellent photosensitivity, bandgap tunability, and solution-processability. However, the only available high-efficiency photodetector (i.e., InGaAs) is expensive to produce via an epitaxial growth process therefore, this photodetector is limited to applications in space exploration and military. The SWIR band is in the range of 1–2.5 µm, which is widely used as a visually safe waveband. The technological advancement of SWIR photodetectors is not only attractive for these diverse applications, but also for the commercialization of technologies that are safe for human eyes. Among the many applications of QDs, short-wave IR (SWIR) photodetectors are widely used in bio-imaging, security, face recognition, food safety inspection, and optical communications. The electrical and optical properties of QDs can be tuned by controlling the size of strong quantum confinement effect. Semiconductor colloidal quantum dots (QDs) are promising candidates for next-generation optoelectronic technologies owing to their unique properties such as their high absorption coefficients, tunable bandgaps, and multiple exciton generation effects. Moreover, the lifetimes of thick-shell PbS/CdS QD-based SWIR photodetectors were significantly improved owing to the self-passivation of QD surfaces. The SWIR photodetectors fabricated using thick-shell PbS/CdS QDs exhibited a high on/off (light/dark) ratio of 11.25 and a high detectivity of 4.0 × 10 12 Jones, which represents a greater than 10 times improvement in these properties relative to those of PbS QDs. In this study, a simple method is proposed to overcome these problems by incorporating CdS in PbS QD shells to provide efficient carrier transfer and enhance the long-term stability of SWIR photodetectors against oxidation. However, the performance of PbS QD-based SWIR photodetectors is limited owing to inefficient carrier transfer and low photo and thermal stabilities. Along with their cost-efficient solution processability and flexible substrate compatibility, PbS QDs are highly interesting for the quantum-size-effect tunability of their bandgaps, spectral sensitivities, and wide absorption ranges. Many researchers have expended considerable efforts to address the problem of SWIR photodetector development using lead sulfide (PbS) quantum dots (QDs). However, the epitaxial process used to grow these materials is expensive therefore, InGaAs-based photodetectors are limited to space exploration and military applications. QD heterostructures harboring bound excitons are therefore excellent candidates for colloidal-based gain devices required to operate in the single exciton gain regime.InGaAs-based photodetectors have been generally used for detection in the short-wave infrared (SWIR) region. By tailoring the nanocrystal’s structure we can thus independently control the emission color, the radiative decay rate and the BX repulsion. The energetics of the BX is shown to be determined mostly by the energy difference between the dopant state and the valence-band edge while the emission color is mostly determined by quantum confinement in the conduction band. The biexciton (BX) is shown to be strongly blueshifted relative to the bound exciton, in stark contrast with the corresponding undoped nanocrystals exhibiting a BX redshift. This is experimentally shown by performing multiexciton spectroscopy of CdSe/CdS and ZnSe/CdS colloidal quantum dot (QD) heterostructures, whose cores are nucleation-doped with few atoms of tellurium, leading to localization of the holes. As we show here, under strong confinement, doping has a dramatic effect on the energetics of multiply excited states, which exhibit a strong size dependence. It is not clear, however, how these effects would change when considering semiconductor nanocrystals in the strong confinement regime. Spatial localization to a defect or a dopant of one of the charge carriers comprising an exciton, has a significant effect on the optical properties of bulk semiconductors. ![]()
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