Constructing Efficient Hole Transport Material through π-Conjunction Extension for Perovskite Solar Cell

Abstract

Efficient hole transport and excellent film formation properties are essential for efficient hole transport materials (HTMs) in perovskite solar cells (PCSs). And, the π-conjugated system and the steric configuration of HTMs can affect charge-carrier mobility and film formation. So, it is feasible to develop efficient HTMs via optimizing the molecular configuration and enlarging the π-conjugation system. Herein, a low-cost spiro[fluorene-9,9′-xanthene] (SFX) core-based HTM, named SFX-DM-DPA, is designed and synthesized through molecular engineering of the efficient HTM SFX-DM by introducing extra 4,4′-dimethoxydiphenylamine units to enlarge the π-conjugation range and to further modulate the charge transport property. The resulting HTM demonstrates enhanced hole extraction/transport efficiency and desired film formation ability. PSCs based on SFX-DM-DPA yielded an impressive efficiency of 22.7%. These results confirmed the importance of precise structural adjustment of the π-conjugated range for developing low-cost and highly efficient HTMs.

A route to carbon-sp3 bridging spiro-molecules: synthetic methods and optoelectronic applications

“…83 To address the issue of the cumbersome synthesis steps involved in spiro-OMeTAD, some researchers have successfully synthesized a series of SFX-based spiro molecules using Xie's one-step reaction method. [84][85][86][87] In Fig. 14b, Xu et al 88 presented the SFX-based structure of the X60 molecule, which was constructed through a two-step reaction.…”

Recent studies on small molecular and polymeric hole‐transporting materials for high‐performance perovskite solar cells

“…The same research group explored spiro[fluorene-9,9 0 -xanthene] (SFX) core-based HTMs. With molecular engineering of the SFX-DM by introducing extra 4,4 0 -dimethoxydiphenylamine units to obtain enlarged π-conjugation, the resulting SFX-DM-DPA-based device showed a smoother film, excellent hole mobility, and larger charge recombination resistance, results a PCE of 22.7% [61]. By extending the central spiro-core fluorinated-SFX with a larger conjugation unit by using the linearization strategy and conjugate engineering, a spiro-type HTM M6-F was reported by Liang et al The doped M6-F-based PSCs exhibited a PCE of 22.17%, whereas the dopant-free M6-F-based PSCs yielded an efficiency of 21.21% [62].…”

Improvement in Dibenzofuran-Based Hole Transport Materials for Flexible Perovskite Solar Cells

“…In addition, the ideal π-conjugated system and the steric configuration of HTMs are crucial in improving their properties. Cheng et al expanded π-conjugations by adding additional 4,4′-dimethoxy-diphenylamine units to HTM based on the spiro [fluoro-9,9′-oxanthracene] (SFX) core [ 14 ], thereby increasing the hole mobility of HTM. Their team also inserted benzene rings into 9,10-dihydroacridine (ACR)-based HTMs to obtain high glass transition temperatures [ 15 ], the highest of which reached 202 °C.…”