Dimeric Self‐Assembled Monolayer Materials for High‐Performance Perovskite and Perovskite/Organic Tandem Solar Cells

ABSTRACT While perovskite/organic tandem solar cells (POTSCs) hold great potential in terms of power conversion efficiencies (PCEs), achieving highly efficient POTSCs remains challenging. A primary bottleneck is the formation of unfavorable buried interfaces and energy level misalignment, often caused by inadequate self‐assembled monolayers (SAMs) on indium tin oxide/nickel oxide (ITO/NiO x ) substrates used for the front perovskite subcell. To address this critical issue, two dimeric SAM materials, named DTh‐4PACz and DPh‐4PACz, were synthesized using thiophene and benzene linkers, respectively, to connect two carbazole‐derived molecules. The DPh‐4PACz‐modified ITO/NiO x substrate exhibits an improved buried interface, leading to wide‐bandgap (WBG) perovskites with enhanced crystallinity and reduced defect density compared to the DTh‐4PACz‐based counterpart. Besides, DPh‐4PACz possesses enhanced conductivity and forms better energy level alignment with the WBG perovskites. Consequently, the best‐performing WBG perovskite solar cell (PSC) based on DPh‐4PACz achieves a higher PCE of 18.78%, compared to 16.77% for the DTh‐4PACz‐based PSC. By integrating the DPh‐4PACz‐based WBG PSC as the front subcell into POTSCs, the resulting device delivers an exceptional PCE of 26.63% (certified at 26.09%). Moreover, the DPh‐4PACz‐based POTSC shows enhanced thermal and light stability. This work provides an effective dimeric SAM material design strategy for efficient and stable PSCs and POTSCs.