Controllable bandgap-gradient halide perovskite films via dip-coating and halide anion exchange for multispectral photodiodes with high performance

Abstract

The perception of light by the human brain involves color and intensity, requiring multispectral photodetectors (PDs) to selectively collect signals from different spectral regions. Achieving high spectral resolution in a single PD is essential for imaging and spectral analysis applications. A strategy combining the dip-coating method and halide anion exchange was proposed to prepare controllable bandgap-gradient halide perovskite films. The gradient bandgap in a specific area can be precisely controlled by modifying the pulling speed and distance. Furthermore, perovskite films with a gradient bandgap ranging from 1.81 eV to 2.66 eV, in which the absorption covered the visible spectrum of 470–695 nm, were realized by dividing the MAPbBr₃ polycrystalline film into two regions and pulling them in MAI and MACl dip-coating solutions respectively. The p–i–n photodiode structure multispectral PD was constructed in one-dimensional bandgap-gradient halide perovskite films, which had continuously varying response cutoff band edges of 480 nm, 570 nm, 640 nm, and 680 nm, respectively. The multispectral PD exhibited a high I_on/I_off ratio of 10⁴–10⁶, a low noise current of 10⁻¹³ A Hz^−1/2 and a short response time of μs magnitude, and RGB multispectral fusion imaging was verified in this device.