Improving buried interface contact by molecular bridging effect for inverted perovskite solar cells

Abstract

The commercial self-assembled monolayer (SAMs) has been shown to significantly enhance the power conversion efficiency (PCE) of inverted (p-i-n) perovskite solar cells (PSCs) when employed as a double hole transport layer (HTL) on nickel oxide (NiO_x). Despite these improvements, the inherent hydrophobicity of the SAMs results in suboptimal crystallization and the formation of micro-scale voids at the buried interface of the perovskite layer, which in turn leads to significant interface defects and serious nonradiative recombination. In this work, we introduce a molecular bridging layer composed of Diethyl (Phthalimidomethyl) phosphonate (DP), characterized by its carbonyl groups and phosphoryl bonds, to be deposited onto the surface of Me-4PACz. This bridging layer demonstrates a remarkable ability to coordinate with lead ions, providing a robust binding affinity that facilitate excellent adhesion to the substrate surface. The synergistic interaction of the two functional groups within the DP layer effectively mitigates bulk-phase defects and suppresses nonradiative recombination at the buried interface of the perovskite. As a result, PSCs incorporating the DP layer achieved a champion PCE of 23.26 % on an active area of 0.09 cm². Additionally, The unencapsulated PSC maintains above 50 % of its initial PCE in the air with a relative humidity (RH) of 50–60 % for 1000 h. This work highlights the potential of integrating bridging layers in optimizing the performance and stability of PSCs.