Isomeric Carbazole-Based Hole-Transporting Materials: Role of the Linkage Position on the Photovoltaic Performance of Perovskite Solar Cells

Abstract

Two structural isomers of carbazole decorated with triarylamine have been designed and synthesized with a facile synthetic procedure. The impact of triarylamine substitution on the isomeric structural linkage of carbazole on the optical, thermal, electrochemical, and photovoltaic properties has been extensively studied by combining experimental and simulation methods. Car­[2,3] showed a red shift in the absorption maximum compared to that of Car­[1,3], indicating the linear conjugation along the 2,7-position of carbazole in the former. The high thermal decomposition temperature (>420 °C) of these compounds could be attributed to the rigid structure of the carbazole core. Perovskite solar cells fabricated with Car­[2,3] as the hole transporting material (HTM) displayed the highest power conversion efficiency (PCE) of 19.23%. It can be attributed to the suitable energy alignment of the highest occupied molecular orbital (HOMO) of HTM with the adjacent perovskite valence band energy level, which results in efficient hole transport. Furthermore, the molecular dynamic simulation demonstrates that the triphenylamine substitution on the 2,3,6,7 positions of Car­[2,3] results in a more planar molecular alignment on top of the perovskite surface, promoting an efficient hole extraction. Essentially, when Car­[1,3] and Car­[2,3] were applied in perovskite solar cells, they showed enhanced long-term stability by retaining >80% of their initial PCEs after 1000 h of continuous illumination.

Interface compatibility: how to outperform classical spiro-OMeTAD in perovskite solar cells with carbazole derivatives

“…22 Finally, strong interactions between selected IL materials and HTMs occur due to chemical compatibility, thereby contributing to hole extraction. Also, carbazole-based molecules are currently among the most promising HTMs, [41][42][43][44][45] and the selected Cz-P and Cz-Pyr HTMs exhibit performances competing and outperforming spiro-OMeTAD. 46,47 In order to investigate the outstanding performance of the IL, planar organic-inorganic lead halide PSCs with the n-i-p architecture were built w/o a polymer IL, as well as reference devices with the standard spiro-OMeTAD as the HTM.…”

Isomeric D‐π‐D Dopant‐Free Hole Transport Materials: Effect of the Substitution Position and Heteroatom on the Performance of Perovskite Solar Cells

“…[22][23][24][25][26][27][28][29]32] Moreover, there are many opposite results about the isomeric or heteroatomic effect. [22][23][24][25][26][27][28][29]33] For example, some reports illustrated that the S-containing HTMs exhibit relatively better device performance than Ocounterparts. [24,26] Some reports illustrate that the carbazole HTMs with peripheral arms on 3,6-position show better device performance than that of 2,7-counterparts.…”

“…[14,[18][19][20][21] Numerous studies have shown that the physicochemical properties of smallmolecular HTMs are tremendously affected by their molecular structures, such as isomeric and heteroatomic effects. [22][23][24][25][26][27][28][29][30][31] Recently, many research groups have investigated the substitution position effect on PSCs' performance, and obtained superior HTMs. [22][23][24][25][26][27][28][29]32] Moreover, there are many opposite results about the isomeric or heteroatomic effect.…”

“…[22][23][24][25][26][27][28][29][30][31] Recently, many research groups have investigated the substitution position effect on PSCs' performance, and obtained superior HTMs. [22][23][24][25][26][27][28][29]32] Moreover, there are many opposite results about the isomeric or heteroatomic effect. [22][23][24][25][26][27][28][29]33] For example, some reports illustrated that the S-containing HTMs exhibit relatively better device performance than Ocounterparts.…”

“…Therefore, many HTMs have been successfully used in PSCs [14,18–21] . Numerous studies have shown that the physicochemical properties of small‐molecular HTMs are tremendously affected by their molecular structures, such as isomeric and heteroatomic effects [22–31] . Recently, many research groups have investigated the substitution position effect on PSCs’ performance, and obtained superior HTMs [22–29,32] .…”