  We develop a device model for pixelless converters of far/mid-infrared
radiation (FIR/MIR) images into near-infrared/visible (NIR/VIR) images. These
converters use polycrystalline graphene layers (PGLs) immersed in the van der
Waals (vdW) materials integrated with light emitting diode (LED). The PGL
serves as an element of the PGL infrared photodetector (PGLIP) sensitive to the
incoming FIR/MIR due to the interband absorption. The spatially non-uniform
photocurrent generated in the PGLIP repeats (mimics) the non-uniform
distribution (image) created by the incident FIR/MIR. The injection of the
nonuniform photocurrent into the LED active layer results in the nonuniform
NIR/VIR image reproducing the FIR/MIR image. The PGL and the entire layer
structure are not deliberately partitioned into pixels. We analyze the
characteristics of such pixelless PGLIP-LED up-converters and show that their
image contrast transfer function and the up-conversion efficiency depend on the
PGL lateral resistivity. The up-converter exhibits high photoconductive gain
and conversion efficiency when the lateral resistivity is sufficiently high.
Several teams have successfully demonstrated the large area PGLs with the
resistivities varying in a wide range. Such layers can be used in the pixelless
PGLIP-LED image up-converters. The PGLIP-LED image up-converters can
substantially surpass the image up-converters based on the quantum-well
infrared photodetector (QWIP) integrated with the LED. These advantages are due
to the use of the interband FIR/NIR absorption and a high photoconductive gain
in the GLIPs.
