Infrared (IR) photodetectors (PDs) are one of many PDs categorized primarily based on the wavelength vary of sunshine absorbed past the seen spectrum, comprising near-infrared (NIR, 0.7 µm to 1.4 µm), short-wave infrared (SWIR, 1.4 µm to three µm), and mid-wave infrared (MWIR, 3 µm to five µm). IR PDs play an important function in PDs know-how with its in depth utilization as a key part in a variety of functions together with telecommunication, medical imaging, environmental monitoring, agriculture, astronomy, client electronics, automotive trade, protection, safety, fiber optics, distant management, night time imaginative and prescient, thermal imaging, wearable well being sensors, IR spectroscopy, fuel evaluation, thermal radiation and warmth detection [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. The seamless integration of IR PDs into numerous functions with utmost effectivity and effectiveness is a testomony to steady growth in IR photodetection know-how [11]. Innovation in IR photodetection know-how is important for harnessing its advantages for repeatedly creating its integration with numerous applied sciences. Furthermore, integrating IR PDs with synthetic intelligence (AI) advances clever knowledge processing, enhancing efficiency and enabling the event of latest functions. The mixing of AI with IR photodetection eases knowledge processing and its evaluation by AI algorithms. The mixing may facilitate the optimization of sensing methods, improve imaging methods, and assist real-time decision-making in numerous domains. The rigorous growth in IR photodetection shows widespread potential for PDs to deal with advanced world challenges and enhance our every day experiences. Fig. 1 reveals the share contribution of complete publications primarily based on Scopus knowledge on numerous potential semiconducting supplies for IR PDs. The IR PDs primarily based on rising supplies, together with perovskites, two-dimensional (2D) supplies, and colloidal quantum dots (CQDs) are being developed as next-generation IR absorbing supplies [12], [13], [14], [15]. The low-cost and solution-processibility of CQDs and their compatibility with silicon-based know-how make them extra reasonably priced and seamless as in comparison with the normal PDs [16]. The wide-spectral tunability of CQDs has a fantastic benefit in using them in keeping with the functions’ necessities. Till now, CQDs-based IR PDs depend on lead-chalcogenides (PbX), InGaAs, InSb, InAsSb, HgTe, and HgCdTe [2], [17], [18]. However the toxicity and environmental impression of Pb, Hg, and Cd primarily based CQDs make the dealing with and their disposal fairly difficult. The environmental persistence of those poisonous supplies results in contamination and bioaccumulation within the meals chain [19], [20]. Latest market evaluation signifies that the worldwide marketplace for CQDs IR detector supplies attained a valuation of roughly USD 412 million in 2024. Forecasts counsel a compound annual progress fee (CAGR) of 17.2 % from 2025 to 2033, with the market anticipated to achieve USD 1482 million by the tip of the forecast interval [21]. This progress is pushed by increasing functions throughout a number of sectors, together with aerospace and protection, healthcare diagnostics, industrial monitoring, and client electronics, the place CQDs-based IR PDs supply enhanced sensitivity, spectral tunability, and miniaturization potential [21].
On this body of reference, binary (Ag2X; X = S, Se, and Te) and ternary silver chalcogenides (AgBiX2) are more and more thought to be lead- and mercury-free options to Pb/Hg-based infrared semiconductors, combining decrease intrinsic toxicity with Restriction of Hazardous Substances (RoHS)-compliant compositions. Binary silver chalcogenides: Ag2S, Ag2Se, and Ag2Te, have emerged as promising supplies for IR optoelectronic functions due to their slim bandgap energies (∼0.15 eV to 1.1 eV). These bandgap values allow robust absorption and emission throughout NIR, SWIR, and MWIR spectral areas. Particularly, Ag2S displays a bandgap of ∼0.9–1.1 eV, Ag2Se ∼0.15 eV, and Ag2Te ∼0.67 eV, positioning them as appropriate candidates for a variety of functions [22], [23], [24]. The Ag2S, Ag2Se, and Ag2Te CQDs possess optical band gaps of as much as 1.5–2.2, 0.8–2.0, and 0.4–1.5 eV, relying on the quantum confinement impact [25], [26], [27]. The Ag2X CQDs are well-explored for bio-medical imaging, photocatalysis, and bio-photonic functions similar to NIR imaging, biosensors, and therapeutics [28]. Equally, amongst ternary silver chalcogenides, AgBiS2 CQDs with favorable charge-transport properties and low value, supply a sustainable platform for next-generation optoelectronic and NIR detection units. AgBiS2 CQDs possess distinctive opto-electronic efficiency, with excessive absorption coefficients (∼105 cm−1) spanning ultraviolet to near-IR wavelengths, a really perfect bandgap for various functions, and sturdy stability throughout steady operation. Lately, CQDs primarily based on Ag2X and AgMX2, have garnered vital consideration for IR PDs functions. Their distinctive bandgap tunability and powerful mild absorption traits current substantial potential for additional growth in high-performance IR photodetection applied sciences. Fig. 1 inset reveals the variety of publications on silver binary and ternary chalcogenide CQDs, demonstrating fast growth for the IR PDs. The event of binary and ternary silver chalcogenide CQDs-based IR PDs is proven in Fig. 2, indicating accelerated developments in recent times.
The proposed overview article focuses on the development of IR PDs using environmentally benign silver chalcogenide CQDs. Given the pivotal function of IR PDs throughout a broad spectrum of functions, world curiosity on this matter is steadily rising. This text presents a complete overview of current developments in IR PDs primarily based on Ag2X CQDs, encompassing a spread of system architectures, together with photoconductors (PC), photodiodes, and phototransistors (PT). The dialogue focuses on the affect of system construction and ligand alternate (LE) methods on key efficiency metrics similar to exterior quantum effectivity (EQE), responsivity, detectivity, and response time. Moreover, the underlying photodetection mechanisms are examined intimately. The useful integration of Ag chalcogenide CQDs IR PDs for superior sensible functions similar to infrared imaging, LiDAR, optical communication, and photoplethysmography has been mentioned in depth. The overview additionally highlights present challenges and future alternatives by evaluating the efficiency traits of assorted Ag2X CQD-based PDs. The article is positioned to serve various and multidisciplinary understanding concerned within the design, analysis, growth, and commercialization of CQD-based IR PDs, providing a well timed synthesis of present progress, current challenges, and future instructions within the subject.
