Fused Furan‐Based Organic Small Molecules as Dopant‐Free Hole Transporting Material for Inverted Perovskite Solar Cells

Abstract

Hole transport material (HTM) is a significant constituent in perovskite solar cells (PSCs). However, HTM generally is not utilized in its pristine form but with dopants (such as lithium salt, tert‐butyl pyridine, F4‐TCNQ), which accelerates device degradation and leads to poor stability. Therefore, dopant‐free HTM is highly desirable to fabricate stable devices. Herein, a fused furan organic small molecule (C8‐DPNDF) is introduced as a dopant‐free HTM in inverted PSCs. As a potential HTM candidate, C8‐DPNDF shows excellent properties, such as high hole mobility, matched energy level with perovskite, and resistance to perovskite precursor solution. As a result, the device based on C8‐DPNDF as HTM shows a power conversion efficiency (PCE) of 17.5%, compared with 17.1% of the control device based on classic poly(bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine) (PTAA) as the HTM. In addition, the unencapsulated device based on C8‐DPNDF as HTM keeps 92% of its initial PCE after 30 days of storage in ambient air with a relative humidity of ≈40%. This finding is expected to pave the way toward stable and highly efficient inverted PSCs based on dopant‐free HTMs.