A Spirobixanthene-Based Dendrimeric Hole-Transporting Material for Perovskite Solar Cells

A dendrimer based on a spirobixanthene core, termed DH1, is designed and synthesized as a hole-transporting material (HTM) for perovskite solar cells (PSCs). DH1 showing a hyperbranched structure with methoxydiphenylamine carbazole dendrons stretching outward along the para-phenylene spacer acquires a large molecular size of up to 1.9 nm, which favors good thermal stability and amorphous property. The thus obtained DH1-based pinhole-free film as a hole-transport layer results in a power conversion efficiency of 17.13% and reduced hysteresis behavior of MAPbI₃-based planar PSCs. This work provides the first example of the use of dendrimer-type HTM for PSC application, demonstrating a promising approach to design HTMs in a quasiglobular dendrimer with a large molecular size.