Open-Circuit Voltage Loss in Lead Chalcogenide Quantum Dot Solar Cells

Lead chalcogenide colloidal quantum dot solar cells (CQDSCs) have received considerable attention due to their broad and tunable absorption and high stability. Presently, lead chalcogenide CQDSC has achieved a power conversion efficiency of approximate to 14%. However, the state-of-the-art lead chalcogenide CQDSC still has an open-circuit voltage (V-oc) loss of approximate to 0.45 V, which is significantly higher than those of c-Si and perovskite solar cells. Such high V-oc loss severely limits the performance improvement and commercialization of lead chalcogenide CQDSCs. In this review, the V-oc loss is first analyzed via detailed balance theory and the origin of V-oc loss from both solar absorber and interface is summarized. Subsequently, various strategies for improving the V-oc from the solar absorber, including the passivation strategies during the synthesis and ligand exchange are overviewed. The great impact of the ligand exchange process on CQD passivation is highlighted and the corresponding strategies to further reduce the V-oc loss are summarized. Finally, various strategies are discussed to reduce interface V-oc loss from charge transport layers. More importantly, the great potential of achieving performance breakthroughs via various organic hole transport layers is highlighted and the existing challenges toward commercialization are discussed.