Constructing a p-π conjugated, phase-pure DJ-type 2D perovskite modification layer to advance the operation stability to 15,160 hours for efficient perovskite solar cells

Abstract

Perovskite solar cells (PSCs) with 2D/3D heterostructures often experience inhibited charge transport capabilities due to the intercalation of long chains of carbon atoms, consequently affecting power conversion efficiency (PCE) of PSCs. Herein, a novel DJ-type 2D perovskite by using 1,1-dimethylbiguanide hydrochloride (DMe-bi-GuaCl), spontaneously forming a vertically oriented phase-pure 2D perovskite modification layer (n=1) via aliphatic diamine cations on 3D perovskites surface. Critically, this work introduces an organic conjugated structure characterized by alternating p-π bonds, that overlaps with the electron clouds of adjacent inorganic octahedral interlayers with its multi-amino groups. It results in continuous vertical charge transport channels that significantly enhance carrier transport, advancing from 0.208 to 2.13 cm²·V^-1·s^-1. This modification layer not only passivates defect sites at the grain boundaries of the 3D perovskite polycrystalline structure but also establishes a hydrophobic barrier through its terminal dimethyl groups and effectively inhibiting halide ion migration. The optimized perovskite films exhibited a notable improved PCE of 23.81% in champion PSC devices. Importantly, the unencapsulated PSCs retained 89% of their initial efficiency after 15,160 hours in ambient conditions along with improved humidity stability under 50±10% relative humidity over 4,200 hours.