Fluorinated Pentafulvalene‐Fused Hole‐Transporting Material Enhances the Performance of Perovskite Solar Cells with Efficiency Exceeding 23%

Abstract

Organic small molecular materials with coplanar π‐conjugated system as HTMs in perovskite solar cells (PSCs) have attracted considerable attention due to their high charge transport capability and thermal stability. Herein, three novel pentafulvalene‐fused derivatives with or without fluorine atoms incorporated (YSH‐oF and YSH‐mF and YSH‐H, respectively) are designed, synthesized, and applied as hole‐transporting materials (HTMs) in PSCs fabrication. The fluorinated HTMs, YSH‐oF and YSH‐mF, exhibited higher hole mobility and better charge extraction at the perovskite/HTM interface than non‐fluorinated one do, presumably due to the closer intermolecular π–π packing interactions. As a result, small‐area (0.09 cm2) PSCs made with YSH‐oF and YSH‐mF achieved an impressive power conversion efficiency (PCE) of 23.59% and 22.76% respectively, with negligible hysteresis, in contrast with the 20.57% for the YSH‐H‐based devices. Furthermore, for large‐area (1.00 cm2) devices, the PSCs employing YSH‐oF exhibited a PCE of 21.92%. Moreover, excellent long‐term device stability is demonstrated for PSCs with F‐substituted HTMs (YSH‐oF and YSH‐mF), presumably due to the higher hydrophobicity. This study shows the great potential of fluorinated pentafulvalene‐fused materials as low‐cost HTM for efficient and stable PSCs.

Modulation of intermolecular interactions in hole transporting materials for improvement of perovskite solar cell efficiency: a strategy of trifluoromethoxy isomerization

“…However, the higher hole mobility of JY6 is likely attributed to the enhanced dipole–dipole interactions between neighboring molecules due to the ortho -position substituted trifluoromethoxy groups, which promote close molecular packing. 48…”

“…However, the higher hole mobility of JY6 is likely attributed to the enhanced dipole-dipole interactions between neighboring molecules due to the ortho-position substituted triuoromethoxy groups, which promote close molecular packing. 48 Through the grazing-incidence wide-angle X-ray scattering (GIWAXS) technique, we conducted a detailed investigation into the molecular stacking of JY4-JY6 lms. Fig.…”

“…This positively inuences the charge transport characteristics and device performance of JY6. [48][49][50] To further investigate the surface morphology of the lms for the designed HTMs, we conducted atomic force microscopy (AFM) measurements. The root mean square roughness (RMS) of the bare perovskite lm surface was the highest at 27.7 nm (Fig.…”

Fluorination on cyclopentadithiophene-based hole-transport materials for high-performance perovskite solar cells

“…The YC-oF and YC-mF show blue-shifted absorption peaks compared with that of YC-H , which may be attributed to the electron-withdrawing inductive effect of the fluorine atoms on the aromatic ring. 12,13 Moreover, the photoluminescence spectra of YC-oF , YC-mF and YC-H show intense emission in the region of 555–564 nm. The optical band gaps ( E g ) of YC-oF , YC-mF , and YC-H were estimated to be 2.37, 2.38, and 2.34 eV, respectively, based on the intersection of normalized UV-vis and PL spectra.…”

“…7–9 In recent years, our group developed a series of CPDT-based HTMs for application in PSCs and achieved excellent PCEs. 10–12 Recently, the introduction of the strong electronegativity of a fluorine atom into the organic conjugated molecule has been proven to be a successful strategy for enhancing photovoltaic properties and stability in PSCs because the fluorination can improve hole transport properties and enhance hydrophobicity. 12,13 However, to the best of our knowledge, the introduction of fluorine atoms into the CPDT backbone as HTMs for PSCs has never been explored.…”