Enhanced Efficiency and Stability for the Inverted High-Bandgap Perovskite Solar Cell via Bottom Passivation Strategy

The bottom perovskite with the hole transport layer (HTL) in inverted perovskite solar cells (PSCs) interface has received little attention due to challenges like interlayer dissolution during perovskite deposition. And voids at the perovskite/HTL interface can degrade cell performance. This work introduces a two-dimensional (2D) perovskite layer between the perovskite and poly (N, N '-bis-4-butylphenyl-N, N '-bisphenyl) benzidine (Poly-TPD) HTL using a mixed solution of 4-methylphenethylammonium chloride (4M-PEA-Cl), methylammonium iodide (MA-I), and Poly(9,9-bis(3 '-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br). The amine functional groups in the organic salts improved HTL wettability, resulting in a void-free interface. 4M-PEA-Cl, with its strong electron-withdrawing benzene ring, outperformed other amine-containing salts in passivating undercoordinated Pb2+ ions. Incorporating this hybrid passivation layer in PSCs resulted in a 1.8% absolute increase in power conversion efficiency (PCE) to 19.1% with 1.68 eV perovskite bandgap. Additionally, the passivated PSCs demonstrated enhanced operational stability, retaining 91% of their initial efficiency after 800 hours of continuous 1-sun illumination, compared to 84.7% for the control sample. This study reveals a novel method to enhance the bottom interface of inverted perovskite solar cells by forming a 2D perovskite layer between the perovskite and hole transport layer. Using an interlayer of 4M-PEA-Cl+MA-I + PFN-Br, the approach eliminates voids, improves wettability, and boosts efficiency to 19.1% with perovskite solar cells retaining 91% initial efficiency after 800 h.image (c) 2024 WILEY-VCH GmbH