Direct Optical Lithography Enabled Multispectral Colloidal Quantum-Dot Imagers from Ultraviolet to Short-Wave Infrared

Complementary metal oxide semiconductor (CMOS) silicon sensors play a central role in optoelectronics with widespread applications from small cell phone cameras to large-format imagers for remote sensing. Despite numerous advantages, their sensing ranges are limited within the visible (0.4–0.7 μm) and near-infrared (0.8–1.1 μm) range , defined by their energy gaps (1.1 eV). However, below or above that spectral range, ultraviolet (UV) and short-wave infrared (SWIR) have been demonstrated in numerous applications such as fingerprint identification, night vision, and composition analysis. In this work, we demonstrate the implementation of multispectral broad-band CMOS-compatible imagers with UV-enhanced visible pixels and SWIR pixels by layer-by-layer direct optical lithography of colloidal quantum dots (CQDs). High-resolution single-color images and merged multispectral images were obtained by using one imager. The photoresponse nonuniformity (PRNU) is below 5% with a 0% dead pixel rate and room-temperature responsivities of 0.25 A/W at 300 nm, 0.4 A/W at 750 nm, and 0.25 A/W at 2.0 μm.


S3. Modification of silicon readout integrated circuits (ROICs)
The proposed multispectral imagers relied on a readout circuit with two types of pixels: a visible pixel to detector the photoluminescence from perovskite QDs and an amplification pixel to integrate photocarriers from HgTe CQDs and convert the charges to voltages. However, silicon readout integrated circuits (ROICs) with such hybrid configuration remain unavailable. Therefore, in our study, we modify a commercially available ROICs to realize such functionalities. The ROICs contains 320×256 amplification pixels with direct injection mode. An integral capacitor is fabricated in each pixel. For a photodiode, it needs two electrodes to connect with the ROICs. The  To modify the ROICs to meet our requirement for the hybrid configuration with visible pixel and amplification pixels, the ground electrode is first patterned and deposited around each pixel electrodes, which eliminate any transportation of photocarriers between adjacent pixels ( Figure. S5b ). Then, transparent and conductive indium Tin oxides (ITO) electrodes are deposited on the ROICs column by column (Figure. S5c). The ITO short the ground and pixel electrodes. Visible photons can pass the ITO contact and will be absorbed by the underlying silicon layers, diodes or field-effect transistors. The visible photons excite carriers, which charge the integral capacitors and form visible images. For the single color imager with provskite QDs, all the pixels are covered with ITO contacts. As shown in Figure. S5d, the modified ROICs can sense visible light and output visible images.

S4. 2.Fabrication process of perovskite CQDs and HgTe CQDs pixels
The multispectral imagers consist of perovskite QDs pixels and HgTe CQDs pixels. Each layer of the deposited HgTe CQDs need to be treated with ethanedithiol (EDT)/HCl in isopropanol (2% volume ratio). As the EDT could significantly quench the photoluminescence of perovskite QDs, HgTe CQDs pixels are fabricated before the perovskite QDs pixels. c. Optical images of ROICs with HgTe CQDs pixels and perovskite QDs pixels. The scale bar is 30μm.
The fabrication process starts from the synthesis of UV-activated HgTe CQDs solution. The 2%wt UV ligands are dissolved in the HgTe CQDs solution. The UV-activated HgTe CQDs solution is then spin-coated onto the modified ROICs, as shown in Figure. S6a. After that, the HgTe CQDs film is then exposed with UV light with dose of 200 mJ through a photomask. After exposure, the HgTe CQDs are developed with Chlorobenzene, resulting in patterned HgTe CQDs pixels. Then, the patterned HgTe CQDs film is then treated with EDT/HCl solution. After EDT/HCl treatment the HgTe CQDs become photoconductive. The spin-coating, UV exposure and developing process can be repeated multiple times until the HgTe CQDs films reach to 300-400 nm in thickness.
The perovskite QDs pixels are fabricated by the same processes of spin-coating, UV exposure, and developing, as shown in Figure. S6b. Figure. S6c shows the optical images of ROICs with HgTe CQDs pixels and ROICs with both HgTe CQDs pixels and perovskite QDs pixels.

S5. Characterization of multispectral imagers
Optical microscope images of the multispectral imager under ambient light and UV light.