Regulating the Solvent Resistance of Hole Transport Layer for High-Performance Inverted Perovskite Solar Cells

The hole transport materials (HTMs) play important roles in transporting holes and regulating perovskite crystallization in inverted perovskite solar cells (PSCs). Concerning the solubility of small-molecule-type HTMs in perovskite precursor solution during fabrication, the strategies including tailoring and crosslinking have been developed. However, how these strategies will influence the solvent resistance of the resultant hole transport layers (HTLs) and the corresponding device performance have not been systematically evaluated. Herein, upon incorporating tailoring and crosslinking groups into diazafluorene backbones, AFL-COOH and AFL-ENE are designed. Compared to the control HTM (AFL-3) with poor solvent resistance and AFL-COOH, the best solvent resistance of crosslinked AFL-ENE (AFL-ENE-CL) film leads to an HTL with the highest quality covered on electrode, which thus results in the lowest trap density, best surface contact, and hole extraction for devices involving the AFL-ENE-CL type HTL and the best power conversion efficiency of 20.8% (20.0% for AFL-COOH, 18.1% for AFL-3). Furthermore, high reproducibility and stabilities also realize for the AFL-ENE-CL-based PSC.

Automated summary

Hole transport materials (HTMs) are crucial for transporting holes and regulating perovskite crystallization in inverted perovskite solar cells (PSCs). Tailoring and crosslinking strategies have been developed to enhance the solvent resistance of HTMs, but their influence on the resulting hole transport layers (HTLs) and device performance has not been systematically evaluated. In this study, AFL-COOH and AFL-ENE HTMs with tailored and crosslinked groups were designed. It was found that the crosslinked AFL-ENE (AFL-ENE-CL) HTL exhibited the best solvent resistance and resulted in a high-quality HTL with low trap density, good surface contact, and efficient hole extraction. The PSCs based on AFL-ENE-CL achieved a power conversion efficiency of 20.8%, demonstrating high reproducibility and stability.