Synergistic Reinforcement of Built-In Electric Fields for Highly Efficient and Stable Perovskite Photovoltaics

Perovskite solar cells (PSCs) have received great attention due to their outstanding performance and their low processing costs. To boost their performance, one approach is to reinforce the built-in electric field (BEF) to promote oriented carrier transport. The BEF is maximized by reinforcing the work function difference between cathode and anode (Delta mu(1)) and increasing the work function difference between lower and upper surfaces of perovskite film (Delta mu(2)) via introduction of electric dipole molecules, denoted as PTFCN and CF3BACl. The synergistic reinforcement of BEF improves charge transport and collection, and realizes markedly high photovoltaic performances with the best power conversion efficiency (PCE) up to 21.5%, a growth of 15.6% as compared to the control device, which is higher than the superposition of improvements achieved by either raising Delta mu(1) or Delta mu(2). Importantly, dual-functional CF3BACl not only supplies dipole effect for tuning the surface potential of perovskite but offers hydrophobic trifluoride group toward the long-term stable unencapsulated PSCs retaining more than 95% PCE after storing 2000 h under ambient conditions. This work demonstrates the synergistic effect of Delta mu(1) and Delta mu(2), providing an effective strategy for the further development of PSC in terms of photovoltaic conversion and stability.