Central-Core Engineering of Dopant-Free Hole Transport Materials for Efficient n-i-p Structured Perovskite Solar Cells

Chang, ZT (Chang, Zhitao)^{[ 1 ]} ; Guo, JH (Guo, Jiahao)^{[ 1 ]} ; Fu, Q (Fu, Qiang)^{[ 1 ]} ; Wang, T (Wang, Ting)^{[ 1 ]} ; Wang, R (Wang, Rui)^{[ 1 ]} ; Liu, YS (Liu, Yongsheng)^{[ 1,2 ]}

SOLAR RRL, 2021, 5(5), 文献号: 2100184

DOI: 10.1002/solr.202100184

摘要

Replacing the dominating and dopant-needing 2,2 ',7,7 '-tetrakis(N,N-di-p-methoxyphenylamino)-9,9 '-spiro-bifluorene (spiro-OMeTAD) with dopant-free organic hole transport materials (HTMs) in n-i-p structured perovskite solar cells (PSCs) is a big challenge. Herein, a class of conjugated organic semiconductor materials, namely, ZT-H1 and ZT-H2, with unfused and fused core units, respectively, are successfully designed and synthesized for dopant-free HTMs. It is found that the HTM ZT-H1 exhibits a hole mobility of 7.08 x 10(-5) cm(2) V-1 s(-1), which is improved to 5.16 x 10(-4) cm(2) V-1 s(-1) for HTM ZT-H2 due to the enlarged molecular planarity of ZT-H2, leading to efficient intermolecular pi-pi interaction. Further investigation indicates that ZT-H2 is more fit to facilitating hole extraction, restraining charge recombination, and guaranteeing long-term stability of the devices. Consequently, a planar n-i-p structured device using ZT-H2 as HTM without any dopants exhibits a remarkable efficiency of 19.63%, which is much higher than that of ZT-H1-based devices (10.64%). Importantly, ZT-H2-based devices are much more stable than the control devices using ZT-H1 or spiro-OMeTAD as the HTM. The findings reveal that the fused central core unit with extended pi-conjugation is an efficient strategy for rationally designing dopant-free HTMs toward stable and efficient PSCs.