Abstract
Shortwave infrared (SWIR) sensors have attracted interest due to their usefulness in applications like military and medical equipment. SWIR sensors based on various materials are currently being studied. However, most SWIR detectors need additional optical filters and cooling systems to detect specific wavelengths. In order to overcome these limitations, we proposed a solution processed SWIR sensor that can operate at room temperature using lead chloride (PbS) QDs as a photoactive layer. Additionally, we adapted zinc oxide (ZnO) nanoparticles (NPs) as an electron transport layer (ETL) to improve the sensitivity of a PbS SWIR sensor. In this study, PbS SWIR sensors with and without a ZnO NPs layer were fabricated and their current–voltage (I–V) characteristics were measured. The on/off ratio of the PbS SWIR sensor with ZnO NPs was 2.87 times higher than that of the PbS SWIR sensor without ZnO NPs at the maximum current difference. The PbS SWIR sensor with ZnO NPs showed more stable current characteristics than that without ZnO NPs because of the ZnO NPs’ high electron mobility and proper lowest unoccupied molecular orbital (LUMO) level.
Highlights
Shortwave infrared (SWIR) sensors are currently used in various applications, including environmental monitoring, military equipment, and medical devices
SWIR optoelectronics technology has been used as the structure for quantum well infrared photodetectors (QWIPs) because of the limitations imposed on integrated devices by the complicated epitaxial growth process of forming quantum dots (QDs) as well as the requirement for cooling devices and additional optic devices for stable operation [6,7,8,9]
Zinc oxide (ZnO) NPs, which are used as an electron transport layer (ETL) in many fields such as light emitting diode (LED) devices and solar cells, can be synthesized at room temperature with facile particle size tuning and effectively transfer the electrons formed in the photoactive layer because of its high electron mobility and appropriate lowest unoccupied molecular orbital (LUMO) level (−4.2 eV) [22,23,24]
Summary
Shortwave infrared (SWIR) sensors are currently used in various applications, including environmental monitoring, military equipment, and medical devices. Zinc oxide (ZnO) nanoparticles (NPs) were used to reduce the high band gap difference between the PbS QDs and the aluminum (Al) electrode, thereby helping to emit electron-hole pairs formed by infrared rays and to improve the sensitivity of the sensor. ZnO NPs, which are used as an electron transport layer (ETL) in many fields such as LED devices and solar cells, can be synthesized at room temperature with facile particle size tuning and effectively transfer the electrons formed in the photoactive layer because of its high electron mobility and appropriate lowest unoccupied molecular orbital (LUMO) level (−4.2 eV) [22,23,24]. The optimized PbS SWIR sensor with ZnO showed an on/off ratio of 3.239 at the maximum current change, which is 2.87 times better than the SWIR sensor using only PbS QDs
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