Review of Narrow‐Bandgap Infrared Quantum Dots Solar Cells

Lead sulfide (PbS) colloidal quantum dots (QDs), which offer advantages such as simple solution processing, low‐cost fabrication, size‐tunable infrared bandgaps, and excellent optoelectronic properties, have emerged as ideal narrow‐bandgap semiconductors for infrared photovoltaic applications. Furthermore, its unique Multiexciton generation (MEG) effect and broad spectral absorption capability enhance infrared photon capture, which in turn boosts photoelectric conversion efficiency (PCE). This review focuses on research progress for PbS QDs solar cells operating in the 1100–1700 nm short‐wave infrared (SWIR) band, corresponding to 1.1–0.7 eV. It summarizes key advancements in material synthesis, surface chemical modifications through ligand exchange and synergistic passivation, and device architecture optimizations like Schottky junctions, heterojunctions, and four‐terminal (4‐T) and two‐terminal (2‐T) tandem structures. A particularly significant strategy involves constructing tandem cells with perovskite materials. This approach has a theoretical efficiency limit of 43%. In terms of certified performance, an efficiency of 26.12% has been achieved in a 4‐T device, while an efficiency of 17.1% has been reached in a 2‐T device. The review prospectively discusses progress in narrower‐bandgap QDs and addresses practical challenges such as defect regulation and large‐scale synthesis. This provides a valuable theoretical and technical reference for developing next‐generation, high‐efficiency infrared solar cells.