Fluorine‐Substituted Benzotriazole Core Building Block‐Based Highly Efficient Hole‐Transporting Materials for Mesoporous Perovskite Solar Cells

Abstract

Two novel donor–accepter–donor structured hole‐transporting materials based on fluorine‐substituted benzotriazole (BTA) core building blocks (2FBTA‐1 and 2FBTA‐2) are designed and synthesized through molecular regulation. Applying these materials into perovskite solar cells, power conversion efficiencies of 7.55% and 17.94% are obtained for 2FBTA‐1 and 2FBTA‐2, respectively. The better photovoltaic performance of 2FBTA‐2 is attributed to its more suitable energy level, more planar molecular configurations, and higher hole mobility. Moreover, the devices with 2FBTA‐2 as hole transport material (HTM) show good stability in air. The results indicate that BTA is a promising building block for future HTM design.

Side-Chain Engineering of Diketopyrrolopyrrole-Based Hole-Transport Materials to Realize High-Efficiency Perovskite Solar Cells

“…7,12 However, the high efficiencies of spiro-MeOTADbased HTMs are often counterbalanced by their complicated fabrication procedure, higher production costs, and lower stability conferred by the presence of hygroscopic dopants such as lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK 209 Co(III)-TFSI). 13,14 Therefore, the replacement of spiro-MeOTAD and the development of new HTMs with superior stability are critical for the development of PSCs.…”

“…In contrast, the D-4 compound was synthesized by the hydrolysis of an initial tert-butyl propionate alkyl side chain followed by acid amide coupling. All the intermediates and final HTMs were characterized by 1 H NMR, 13 C NMR, and mass spectrometry, and their detailed synthetic procedures are provided in the Supporting Information. All the newly prepared HTMs demonstrated good solubilities in commonly used organic solvents, such as chloroform, tetrahydrofuran, and CB, thereby ensuring their good processabilities.…”

“…However, current research trends shows that the researchers have paid considerable attention to the passivation of defects in the bulk and/or interface between the HTM and the light-harvesting perovskite material in order to boost the performance of the PSCs. As charge-transport properties of the HTMs mainly depend upon the structure of the π-conjugated backbone and the nature of the attached functional groups, numerous HTMs have been designed and synthesized with various conjugated cores, such as thiophene, phenol, 15 pyrene, 16 dithienopyrrole, 17,18 dibenzoquinquethiophene, 19 cyclopentadithiophene, benzotriazole, 13 bithiophene imide, 5 fluorene, 12,20,21 and triazines. Over the years, diketopyrrolopyrrole (DPP) has evolved as a promising acceptor moiety due to its distinct advantages, including a rigid molecular structure, strong light absorption, excellent photochemical stability, and facile synthetic modification.…”

“…Meanwhile, hole-transport materials (HTMs), which can simultaneously facilitate hole transfer and enhance stability, play a significant role in enhancing the photovoltaic (PV) performance of all the developed PSC architectures. ,, Among the efficient HTMs reported to date for the n–i–p structure, the spiro-based organic semiconductor 2,2′,7,7′-tetrakis-[ N , N′ -di­(4-methoxyphenyl)­amine]-9,9′-spirobifluorene (spiro-MeOTAD) is commonly used in most PSCs due to its outstanding efficiency. , However, the high efficiencies of spiro-MeOTAD-based HTMs are often counterbalanced by their complicated fabrication procedure, higher production costs, and lower stability conferred by the presence of hygroscopic dopants such as lithium bis­(trifluoromethanesulfonyl)­imide (Li-TFSI) and tris­(2-(1 H -pyrazol-1-yl)-4- tert -butylpyridine)­cobalt­(III) tri­[bis­(trifluoromethane)­sulfonimide] (FK 209 Co­(III)-TFSI). , Therefore, the replacement of spiro-MeOTAD and the development of new HTMs with superior stability are critical for the development of PSCs.…”

Surface Defect Passivation and Energy Level Alignment Engineering with a Fluorine-Substituted Hole Transport Material for Efficient Perovskite Solar Cells

“…Here, the perovskite layer was deposited by using the one-step spin-coating method as previously reported. 36 2FBTA-1 was introduced into the device by adding 2FBTA-1 into an antisolvent during the perovskite film spincoating process. First, the concentration of 2FBTA-1 in the antisolvent was optimized.…”