Abstract
Colloidal quantum dots (CQDs) have attracted tremendous research interests in future-generation energy, electronic, optoelectronic, and bio-imaging applications due to their fascinating material properties, such as solution processability at room temperature and under ambient conditions, compatibility with various functional materials, and high photostability as well as photosensitivity. Among the various optoelectronic applications of CQDs, optical light sensors, which convert photonic energy into electrical signals, have been of particular interest because they are one of the key building blocks for modern communication and imaging applications, including medical X-ray and near-infrared imaging, visible light cameras, and machine vision. However, CQDs, which have been widely researched for photodetectors (PDs) so far, contain toxic and hazardous heavy metals, namely, lead (Pb), cadmium (Cd), and mercury (Hg). These substances are extremely toxic and harmful to the environment as well as human beings. Therefore, it is highly desirable to substitute CQDs containing heavy metals with nontoxic and environmentally friendly ones to realize green optoelectronics. In this review article, we introduce various kinds of heavy metal–free CQDs and their PD applications. This article comprehensively includes working mechanisms of PDs, various kinds of nontoxic and environmentally friendly CQD-based PDs, advanced heterojunction PDs, and discussion for future perspectives.
Highlights
With the rapid development of science and technology, optoelectronic devices, such as photovoltaic systems (PVs), photodetectors (PDs), light-emitting diodes (LEDs), and lasers, have become indispensable parts of the modern society
The performance of PDs based on heavy metal–free Colloidal quantum dots (CQDs) has been significantly enhanced through material engineering and device structure optimization
This review introduced the recent advances of state-of-the-art PDs based on toxic and hazardous heavy metal–free CQDs
Summary
With the rapid development of science and technology, optoelectronic devices, such as photovoltaic systems (PVs), photodetectors (PDs), light-emitting diodes (LEDs), and lasers, have become indispensable parts of the modern society. Li et al (2019) reported a multilayer PD by sandwiching perovskite cesium lead bromide (CsPbBr3) QDs between two organic layers In this device configuration, the heterojunction between organic materials and QDs contributed to the suppression of dark current and the enhancement of photocurrent, resulting in high sensitivity of PDs. Despite the superior device performance, presence of toxic heavy metals in QDs raises serious environmental and health issues, such as leakage of toxic and hazardous elements in the environment, workplace incidences during fabrication processes, and unsafe use of devices in indoor environments. A gate voltage is applied to modulate the conductivity of the channel and suppress the dark current In this device structure, the device exhibits high sensitivity because large photoconductive gain and low noise can be achieved at the same time
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