Hydrogen chloride treated InAs quantum dot thin film phototransistor for ultrahigh responsivity

Indium Arsenide (InAs) colloidal quantum dots (CQDs) are emerging candidates for infrared photodetector applications owing to their excellent optoelectronic properties and low toxicity. However, low electron mobility stemming from its unique surface chemistry hinders its practical application. Through comprehensive structural and chemical analyses, we optimized the one-step HCl treatment to achieve stoichiometric balance, a well-passivated surface with low defect density, and an improved coupling effect by reducing the interparticle distance. Subsequently, a near infrared photodetector at a wavelength of 980 nm was fabricated with the modified InAs QDs in thin film transistor structure by all-solution process, showing remarkable electron mobility enhancement of up to 3.15 cm²/V∙s. The thin film phototransistor exhibited excellent photoresponse with a responsivity of 5.45 × 10³ A/W, external quantum efficiency of 6.90 × 10⁵%, and a linear dynamic range of 50 dB. This achievement represents the highest responsivity observed in an InAs QD-based phototransistor device, demonstrating its potential for lead-free infrared (IR) region optoelectronic applications.