Abstract
InGaAs-based photodetectors have been generally used for detection in the short-wave infrared (SWIR) region. However, the epitaxial process used to grow these materials is expensive; therefore, InGaAs-based photodetectors are limited to space exploration and military applications. Many researchers have expended considerable efforts to address the problem of SWIR photodetector development using lead sulfide (PbS) quantum dots (QDs). 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. However, the performance of PbS QD-based SWIR photodetectors is limited owing to inefficient carrier transfer and low photo and thermal stabilities. 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. 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 × 1012 Jones, which represents a greater than 10 times improvement in these properties relative to those of PbS QDs. Moreover, the lifetimes of thick-shell PbS/CdS QD-based SWIR photodetectors were significantly improved owing to the self-passivation of QD surfaces.
Highlights
Semiconductor colloidal quantum dots (QDs) are promising candidates for next-generation optoelectronic technologies [e.g., light-emitting diodes (LEDs), visible and infrared (IR) photodetectors, and photovoltaic (PV) devices] [1,2,3,4,5] owing to their unique properties such as their high absorption coefficients, tunable bandgaps, and multiple exciton generation effects [6,7,8,9]
The excellent stability of the provided by lead sulfide (PbS)/CdS QD-based short-wave infrared (SWIR) photodetector (SWIR PD3) is attributed to the efficient QD passivation afforded by the thick CdS shell, which serves as a physical barrier to the penetration of oxygen
4 Conclusions In conclusion, we designed, fabricated, and optimized a solution process for a SWIR photodetector that was based on type-I core/shell PbS/CdS QDs
Summary
Semiconductor colloidal quantum dots (QDs) are promising candidates for next-generation optoelectronic technologies [e.g., light-emitting diodes (LEDs), visible and infrared (IR) photodetectors, and photovoltaic (PV) devices] [1,2,3,4,5] owing to their unique properties such as their high absorption coefficients, tunable bandgaps, and multiple exciton generation effects [6,7,8,9]. For practical application in commercial products, QDs are required to have good photo and thermal stabilities These properties, along with device performance, have recently been improved by coating an inorganic CdS shell onto a PbS core [26,27,28]. To improve the charge transfer and stability of QDs, this study focuses on the synthesis of a type-I core/shell structure and its induced CdS passivation on the PbS QD surface. By analyzing passivated QDs, we confirmed the photostability and the efficient carrier dynamics and improved lifetime of SWIR photodetectors To evaluate their performance, we fabricated solution-processable SWIR photodetectors by employing a modification of previously reported methods [38]
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