Perovskite-Based Upconversion Materials for Solution-Processed Silicon-Based Near-Infrared Detectors

Solution-processed rare-earth based upconversion materials support anti-Stokes processes leading to conversion of low-energy photons through the presence of a sensitizer facilitating resonant energy transfer. Traditional lanthanide-based upconversion materials (~ NaYF₄:X:Y) exhibit sensitivity at specific infrared wavelengths owing to strict selection rules permitting 4f-4f transitions. In this work, we report on the synthesis of perovskite material, CsPbBr₃ which is used as an upconversion thin film for silicon-based lost-cost detectors. X-ray diffraction (XRD, Rigaku Miniflex) was used to verify successful synthesis of the orthorhombic phase[1] of CsPbBr₃nanoparticles, with a particle size of 14 nm estimated by transmission electron microscopy (TEM, FEI Tecnai TF20). Absorbance (Perkin Elmer Lambda 1050) data reveals a peak at 507 nm, which correlates to an estimated optical band gap ~2.38 eV derived from the Tauc plot. Excitation at multiple infrared wavelengths (range: 700 nm to 850 nm) results in upconverted green emission peaks (~ 522 nm), attaining maximum upconversion photoluminescence (UCPL) intensity at 850 nm (photon count: 2.29 x 10⁵ photons) with a monotonic decrease in photon count with increase in energy (photon count: 6.89 x 10³ photons at 700 nm). To prove the viability of the retrofitting approach, the perovskite film was spin-coated (APEX IC NXG-P2) on a glass slide and then placed inverted over a lost-cost commercial detector (~ $5, Amazon.in, QE=5.7% at 460 nm). Preliminary third quadrant measurements reveal a measured short-circuit photocurrent of 0.35 μA/cm² at 800 nm excitation (0.21 mW), with a sub-linear incident power dependence. Measured responsivity increases by 3.03% at 575 nm, with comprable increases in specific regions (550 nm to 650 nm) of the incident spectrum when the perovskite layer on glass is retrofiited with the detector. These results suggest that perovskite-based upconversion thin films can be viable for increasing the broadband response of Si-based photodetectors in the near-infrared band.<br/><br/>[1]Hassan et al, ACS Appl. Mater. Interfaces, 2020, 12, 7317-7325.