Infrared PbS Quantum Dot–Lead Halide Perovskite Combinations for Breaking the Shockley–Queisser Limit

Lead sulfide (PbS) quantum dots (QDs) and lead halide perovskites (LHPs) have emerged as highly promising materials for high-efficiency photovoltaics. PbS QDs offer size-dependent bandgaps in the infrared region and the potential for multiple exciton generation, while LHPs feature tunable bandgaps, high absorption coefficients, and long carrier diffusion lengths in the visible spectrum. This review focuses on two primary approaches to breaking the Shockley–Queisser (S–Q) limit based on the combinations of these two semiconducting materials: 1) monolithic 2-terminal tandem photovoltaics with complementary spectral absorption; and 2) intermediate-band solar cells (IBSCs) leveraging PbS QDs within a LHP matrix. Due to the ideally complementary spectrum of PbS and LHPs, emphasis is placed on the prevailing strategies for enhancing efficiency, addressing the major challenges in rational materials designs and device optimizations. Then, key obstacles including surface passivation, solvent compatibility, and the limited performance of small-bandgap PbS QD solar cells are analyzed, along with various potential solutions for tandem cells. For IBSCs, the evolution of materials and device architecture and the unique advantages of their combination are outlined in detail. Finally, this review provides a comprehensive outlook on future research directions to develop efficient tandem and IBSC devices for breaking the S–Q limit.