Selenophene‐Based Hole‐Transporting Materials for Perovskite Solar Cells

Abstract

Two novel and simple donor-π-bridge-donor (D-π-D) holetransporting materials (HTMs) containing two units of the pmethoxytriphenylamine (TPA) electron donor group covalently bridged by means of the 3,4-dimethoxyselenophene spacer through single and triple bonds are reported. The optoelectronic and thermal properties of the new selenium-containing HTMs have been determined using standard experimental techniques and theoretical density functional theory (DFT) calculations. The selenium-based HTMs have been incorporated in mesoporous perovskite solar cells (PSCs) in combination with the triple-cation perovskite [(FAPbI 3 ) 0.87 (MAPbBr 3 ) 0.13 ] 0.92 [CsPbI 3 ] 0.08 . Limited values of power conversion efficiencies, up to 13.4 %, in comparison with the archetype spiro-OMeTAD (17.8 %), were obtained. The reduced efficiencies showed by the new HTMs are attributed to their poor film-forming ability, which constrains their photovoltaic performance due to the appearance of structural defects (pinholes).

Selenium: A Unique Member in the Chalcogen Family for Conjugated Materials Used in Perovskite and Organic Solar Cells

“…[ 24 ] Nazeeruddin and co‐workers also reported two donor–π‐bridge–donor (D–π–D) HTMs, TPASe‐1 and TPASe‐2 (Figure 2), choosing 3,4‐dimethoxyselenophene as the spacer and TPA as the electron‐donating unit, linked covalently through a single bond or an acetylene bridge. [ 25 ] However, the PCEs of the PVSCs using these HTMs are lower than that of spiro‐OMeTAD‐based devices, which are caused by the poor film formation ability of the transporting materials which induced pinhole formation on the perovskite layer.…”

Hole-transport materials based on the terthienyl core unit for efficient perovskite solar cells

“…16–24 Therefore, many researchers have expended great efforts to develop a low-cost HTM to replace spiro-OMeTAD. 25–31…”

“…[16][17][18][19][20][21][22][23][24] Therefore, many researchers have expended great efforts to develop a low-cost HTM to replace spiro-OMeTAD. [25][26][27][28][29][30][31] Oligothiophenes, as a part of the building blocks in HTMs, present an electron-rich nature due to containing S atoms, further facilitating the improvement of the intramolecular interactions and charge dissociation as well as the conductivity of HTM material. [32][33][34][35] Based on these benefits, we designed and synthesized two HTMs, adopting the terthienyl (TTP) unit as the core building block and triphenylamine or 4,4 0dimethoxydiphenylamine as the end-capping groups, and termed them THP-1 and THP-2, respectively (see Fig.…”

Dimers of diethynyl-conjugated zinc-phthalocyanine as hole selective layers for perovskite solar cell fabrication

“…The inclusion of the triple bonds along the π-linker in the ZnPc dimers allows co-planarity in the molecular core structure of the HTMs. 34 ZnPc 2 is a simplify structure with two contiguous triple bonds as linkers of both ZnPc macrocycles. In this context, to obtain a 3D structure, we designed a new dimer containing 2',7'-diethynylfluorene as the linker element (ZnPc 3).…”

“…The inclusion of triple bonds along the p-linker in the ZnPc dimers allows co-planarity in the molecular core structure of the HTMs. 34 ZnPc 2 is a simplified structure with two contiguous triple bonds as linkers of both ZnPc macrocycles.…”