Highly Efficient (9) Lead-Free AgBiS_2 Colloidal Nanocrystal/Organic Hybrid Solar Cells

摘要

Environmentally friendly colloidal nanocrystals (NCs) are promising materialsfor next-generation solar cells because of their low cost, solution processability,and facile bandgap tunability. Recently, silver bismuth disulfide(AgBiS_2) has attracted considerable attention owing to its appreciable powerconversion efficiency (PCE) of 6.4. However, issues such as the low opencircuitvoltage (VOC) compared to the bandgap of the AgBiS_2 NCs and theunoptimized energy level structure at the AgBiS_2 NC/PTB7 hole-transportinglayer (HTL) interface should be resolved to enhance the performance of solarcells. In this study, a design strategy to obtain efficient energy level structurein AgBiS_2 NC/organic hybrid solar cells is proposed. By selecting PBDB-T-2Fas an HTL with a lower highest occupied molecular orbital level than that ofPTB7, the V_（OC） of the device is increased. Furthermore, iodide- and thiolatepassivatedAgBiS_2 NC surfaces are generated using tetramethylammoniumiodide (TMAI) and 2-mercaptoethanol (2-ME), which leads to the energylevel optimization of NCs for efficient charge extraction. This improves thePCE from 3.3 to 7.1. In addition, the polymer is replaced with a PBDB-T-2F:BTP-4Cl blend to achieve a higher short-circuit current density throughcomplementary absorption. Accordingly, an AgBiS_2 NC-based solar cell with aPCE of 9.1 is fabricated.