Abstract
The strong quantum confinement effect in lead selenide (PbSe) colloidal quantum dots (CQDs) allows to tune the bandgap of the material, covering a large spectral range from mid- to near infrared (NIR). Together with the advantages of low-cost solution processability, flexibility and easy scale-up production in comparison to conventional semiconductors especially in the mid- to near infrared range, PbSe CQDs have been a promising material for infrared optoelectronic applications. In this study, we synthesized monodisperse and high purity PbSe CQDs and then demonstrated the photodetectors working at different wavelengths up to 2.8 µm. Our high quality PbSe CQDs show clear multiple excitonic absorption peaks. PbSe CQD films of different thicknesses were deposited on interdigitated platinum electrodes by a simple drop casting technique to make the infrared photodetectors. At room temperature, the high performances of our PbSe CQD photodetectors were achieved with maximum responsivity, detectivity and external quantum efficiency of 0.96 A/W, 8.13 × 109 Jones and 78% at 5V bias. Furthermore, a series of infrared LEDs with a broad wavelength range from 1.5 μm to 3.4 μm was utilized to demonstrate the performance of our fabricated photodetectors with various PbSe CQD film thicknesses.
Highlights
Colloidal quantum dots (CQDs) have been studied extensively due to their attractive optoelectronic properties such as high luminescence efficiency, large dipole moment, strong light absorption, good photo-stability, and multiple electron hole pair generation [1,2,3,4]
We report about high performance photodetectors at a broad spectral range, for the first time, up to 2.8 μm based on our high quality, monodisperse PbSe CQDs
The size distribution and the corresponding Gaussian curve fitting for the synthesized PbSe CQDs are shown in Fig. 1(b), in which the results were analyzed from more than 100 nanoparticles
Summary
Colloidal quantum dots (CQDs) have been studied extensively due to their attractive optoelectronic properties such as high luminescence efficiency, large dipole moment, strong light absorption, good photo-stability, and multiple electron hole pair generation [1,2,3,4]. The strong quantum confinement effect allows us to tailor the energy band gap of these materials by controlling their size in a cost-effective wet chemical synthesis [5,6,7]. These advantages bring CdSe-based CQDs to a competitive market of lighting and display technology today. Mcdonald et al [34] studied solution processed PbS CQD infrared photodetectors and reported the responsivity as 3.1 mA/W for 975 nm illumination These PbS CQD photodetectors for near infrared spectrum only reach around 1.7 μm wavelength [35], the transition range between NIR and SWIR
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