Multifunctional Cross-Linked Hole Transporting Interfacial Layer for Efficient and Stable Perovskite Solar Cells

The efficiency and long-term stability of perovskite solar cells are severely limited by the challenges of the surface defects and the perovskite degradation caused by moisture and Li+ diffusions. To overcome these disadvantages, a multifunctional cross-linked interfacial layer of poly(V-TPAFDPA-co-PETMP) by copolymerization of V-TPAFDPA and PETMP is introduced between the Cs0.05(FA0.83MA0.17)0.95Pb(Br0.17I0.83)3 perovskite and the hole transport layer (HTL). The unique cross-linked structure incorporates the highly conjugated units from V-TPAFDPA benefiting hole extraction and moisture prevention, as well as the −S– and C═O groups from PETMP for surface defect passivation. Moreover, the cross-linked network shows improved stability against the subsequent solvent treatment for HTL preparation and Li+ penetration. An ameliorated power conversion efficiency from 20.18 to 21.19% is achieved with the cross-linked interlayer, and the long-term stability under moisture, illumination, or elevated temperature is also improved, which highlights our effective design on the multirole cross-linked interfacial materials.