Organic and colloidal quantum dot (CQD) absorber materials are increasingly recognized as transformative candidates for thin-film NIR and SWIR photodetectors, offering unique benefits such as spectral tunability, scalability for large-area fabrication, mechanical flexibility, and compatibility with solution-based processing [1-3]. These materials provide a compelling alternative to traditional III-V semiconductors, particularly when integrated monolithically with state-of-the-art silicon read-out circuits (ROICs). This approach eliminates the need for flip-chip bonding, significantly reducing manufacturing costs while enabling smaller pixel pitches and minimizing optical crosstalk [1-3]. Such advances have already enabled SWIR imaging systems with the smallest pixel pitch and highest resolution [4].

Among CQD materials, PbS stands out as the most widely used SWIR absorber, owing to its favorable quantum confinement properties, tunable energy band structures, and extensive progress in synthesis and ligand engineering [5]. Despite this success, the search for heavy-metal-free alternatives has been a long-standing goal. Recent breakthroughs in the synthesis and surface passivation of InAs CQDs have positioned them as a promising option [6-7]. Organic absorbers, although limited to NIR detection, achieve ultralow dark current and high detectivity, making them invaluable for niche applications and further development toward SWIR detection [8].

The thin-film photodiodes (TFPDs) developed in this work are engineered for integration with CMOS ROIC and optimized for specific spectral regions. Their layered architecture includes electron transport layer, CQD (PbS and InAs) or organic absorber layer, hole transport layer, and ITO electrode. These devices utilize pixelated metal electrodes to interface with ROIC, converting photogenerated charge into electronic signals for image processing. Fabricated on a 130 nm CMOS platform, the thin film NIR and SWIR imagers feature 5 μm pixel pitch and a 512×768-pixel focal plane array. The bonded and packaged imager chips were evaluated under halogen illumination and contrast profiles were compared with visible imagers.

Thanks to the unique material specific reflection properties, captured image exhibits distinct contrasts for different materials which are absent under visible imaging. Benefitting from the ultralow dark current in organic bulk hetero junction structure the NIR OPD imagers demonstrate high signal-to-noise ratio and a specific detectivity (D*) of 2.25×10¹³ Jones at 905 nm. The D* of PbS and first generation heavy-metal-free InAs SWIR imager are 4.3×10¹¹ Jones at 1420 nm and 7.4×10⁹ Jones at 1340 nm, respectively. These results establish a foundation for the design of next-generation thin-film SWIR imaging systems, offering a sustainable, high-performance alternative to conventional technologies. These results establish a foundation for designing next-generation cutting-edge thin-film SWIR imagers, expanding their reach from niche markets to broader applications in consumer electronics.