Improved Hole-Transporting Property via HAT-CN for Perovskite Solar Cells without Lithium Salts

Abstract

A nonadditive hole-transporting material (HTM) of a triphenylamine derivative of N,N'-di(3-methylphenyl)-N,N'-diphenyl-4,4'-diaminobiphenyl (TPD) is used for the organic-inorganic hybrid perovskite solar cells. The power conversion efficiency (PCE) can be significantly enhanced by inserting a thin layer of 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HAT-CN) without adding an ion additive because the hole-transporting properties improve. The short-circuit current density (J(sc)) increases from 8.5 to 13.1 mA/cm(2), the open-circuit voltage (V(oc)) increases from 0.84 to 0.92 V, and the fill-factor (FF) increases from 0.45 to 0.59, which corresponds to the increase in PCE from 3.2% to 7.1%. Moreover, the PCE decreases by only 10% after approximately 1000 h without encapsulation, which suggests an alternative method to improve the stability of perovskite solar cells.

Dopant‐Free Hole Transporting Materials for Perovskite Solar Cells

“…Without using any dopants, PCEs up to 12% have been achieved for perovskite devices with mesoscopic architecture. In a study, Ma et al have used N,N′‐di(3‐methylphenyl)‐N,N′diphenyl‐4,4′‐diaminobiphenyl (TPD) ( 47 ) as the HTM of PSC and without using any dopants, a low efficiency of 3.2% has been obtained . However, employing 1,4,5,8,9,11‐hexaazatriphenylenehexacarbonitrile (HAT‐CN), as a buffer layer between HTM and Au electrode, with the optimum thickness of 3 nm, has improved the PCE up to 7.1%.…”

Research Update: Strategies for improving the stability of perovskite solar cells

“…29 Removing the need for external dopants can also be achieved by synthesizing novel hole-transport materials which have tailored energy levels and inherently good charge transport characteristics and therefore do not require additional doping for efficient charge extraction. 22,24,25,27,30 Promising results were obtained by Kim et al, employing a newly synthesized polymer as hole-transporter which was shown to protect the perovskite absorber for 1400 h at 75% relative humidity in the dark and at room temperature ( Fig. 1(c)).…”

Open-shell doublet character in a hexaazatrinaphthylene trianion complex

“…[5][6][7] Metal-free HAT derivatives can display liquid crystal behaviour, 8 which, in tandem with their electron transport and semiconductor properties, 9 has introduced potential uses in organic electronics. [10][11][12][13][14][15] Electron-deficient HAT derivatives have also been used for anion recognition applications. 16 The ability of HAT-type ligands to bind up to three transition metal ions is of interest in the context of molecular magnetism.…”