Recent Progress in Bulk Heterojunction Solar Cells: Emerging Strategies for High Performance

Bulk Heterojunction (BHJ) solar cells integrate photoactive polymers with quantum dots (QDs) or nanocrystals (NCs) to synergistically combine the advantages of organic and inorganic materials. This hybrid architecture facilitates efficient charge transport and significantly enhances light absorption across the solar spectrum. The tunable optical and electronic properties of NCs allow flexible design strategies to maximize photon capture over a broad wavelength range. In particular, lead chalcogenide-based NCs (PbS, PbSe, PbTe) are notable for their strong near-infrared (NIR) absorption and size-dependent bandgap tunability ranging from 0.3 to 1.5 eV, attributed to their large exciton Bohr radii of approximately 18, 46, and 150 nm, respectively. Despite their promising optoelectronic features, the incorporation of lead chalcogenide NCs into polymer-based BHJ architecture remains relatively underexplored. This review highlights recent progress in the integration of these NCs within polymer composites, examines their influence on material properties and device performance, and discusses existing challenges and future research directions for advancing BHJ solar cell technology. Keywords: BHJ Solar Cells; Quantum Dots; Lead Chalcogenides; Bandgap Tuning; NIR Absorption