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

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.