Rational composition engineering for high-quality Pb–Sn photodetector toward sensitive near-infrared digital imaging arrays

Broadband photodetectors (PDs) capable of multi-wavelength detection have garnered significant interest for applications in environmental monitoring, optical communication, spectral analysis, and imaging sensing. Low-bandgap Pb–Sn hybrid perovskite photodetectors can extend the spectral response from the ultraviolet–visible (UV–vis) range to the near-infrared (NIR) and reduce the toxicity associated with Pb 2+ . The strategic introduction of Sn 2+ into Cs 0.15 FA 0.85 Pb x Sn 1− x I 3 ( x = 1, 0.8, 0.6, 0.5, 0.4, 0.2, and 0) not only preserves the cubic crystal structure with conformal multigrain growth but also broadens the film's absorption spectrum from 800 to 1000 nm NIR region. This indicates a well-controlled tunability of the Pb–Sn binary perovskite system. Specifically, the self-powered photodetector with a device structure of ITO/NiO x /PTAA/Cs 0.15 FA 0.85 Pb 0.5 Sn 0.5 I 3 /PCBM/BCP/Ag has shown remarkable optoelectrical properties. It exhibits a high external quantum efficiency (EQE) of up to 80% across the spectrum from 300 to 1000 nm, a responsivity ( R ) exceeding 0.5 A/W, and high detectivity ( D *) value of 1.04 × 10 12 Jones at 910 nm and 3.38 × 10 11 Jones at 1000 nm after weak attenuation. Intriguingly, the dark current of the Cs 0.15 FA 0.85 Pb 0.5 Sn 0.5 I 3 device is four orders of magnitude lower than that of devices made with pristine Pb or Sn only, strongly correlating with its significantly increased built-in potential and reduced trap density. Consequently, it demonstrates a −3 dB bandwidth of 2.23 × 10 4 Hz, fast rise and decay times of 61 and 30 μs, respectively, and a linear dynamic range (LDR) of 155 dB. Benefiting from its high sensitivity, a 5 × 5 PD array for NIR imaging and non-invasive pulse detection for photoplethysmography applications has been successfully demonstrated, showcasing the prosperous potential of Pb–Sn hybrid perovskite in the NIR range.