Compact Hole-Selective Self-Assembled Monolayers Enabled by Disassembling Micelles in Solution for Efficient Perovskite Solar Cells

Self-assembled monolayers (SAMs) are widely employed as effective hole-selective layers (HSLs) in inverted perovskite solar cells (PSCs). However, most SAM molecules are amphiphilic in nature and tend to form micelles in the commonly used alcoholic processing solvents. This introduces an extra energetic barrier to disassemble the micelles during the binding of SAM molecules on the substrate surface, limiting the formation of a compact SAM. To alleviate this problem for achieving optimal SAM growth, a co-solvent strategy to disassemble the micelles of carbazole-based SAM molecules in the processing solution is developed. This effectively increases the critical micelle concentration to be above the processing concentration and enhances the reactivity of the phosphonic acid anchoring group to allow densely packed SAMs to be formed on indium tin oxide. Consequently, the PSCs derived from using MeO-2PACz, 2PACz, and CbzNaph SAM HSLs show universally improved performance, with the CbzNaph SAM-derived device achieving a champion efficiency of 24.98% and improved stability. The co-solvent strategy to disassemble the micelles formed by the amphiphilic self-assembled monolayer (SAM) molecules is introduced. The pre-disassembly of micelles reduces the energetic barrier to form a densely packed SAM. This strategy universally enhances the power conversion efficiencies (PCEs) of PSCs based on MeO-2PACz, 2PACz, and CbzNaph SAM hole-selective layers. The champion device based on the CbzNaph processed from co-solvent achieves a high PCE of 24.98% with an impressive fill factor of 85.06%.image

Automated summary

An introduced co-solvent strategy is utilized to disassemble the micelles formed by amphiphilic self-assembled monolayer (SAM) molecules, reducing the energetic barrier for densely packed SAM formation and universally enhancing the power conversion efficiencies (PCEs) of PSCs using MeO-2PACz, 2PACz, and CbzNaph SAM hole-selective layers. The champion device processed from CbzNaph using this co-solvent achieves a high PCE of 24.98% and improved stability.