Exploration of the Effect of Fluoridation on the Doping-Free Linear Dibenzothiophene-Based Hole-Transport Material Applied for Inverted Perovskite Solar Cells

Abstract

The utilization of hole-transport materials (HTMs) in perovskite solar cells (pero-SCs) is essential for the betterment of hole extraction and hole transport, both of which are critical for enhancing efficiency. To commercialize pero-SCs, the improvement in highly efficient and cost-effective HTMs without dopants is essential. As the HTMs used in inverted pero-SCs, two dibenzothiophene (DBT)-based small linear compounds, denoted DBT-MOP (with the methoxyphenyl in the peripheral) and DBT-2F-MOP (with fluorinated methoxyphenyl in one branch), are designed and synthesized in this study. Compared to fluorinated DBT-2F-MOP, DBT-MOP shows an amorphous state, increasing hole-transport mobility, and greater charge extraction; thus, the inverted device based on DBT-MOP exhibits a remarkable efficiency of 19.5%, while the devices based on DBT-2F-MOP show an efficiency only reaching up to 15.19%. The efficiency of the DBT-MOP-based devices is among the top efficiencies of the DBT-based HTMs. However, the introduction of the fluoride atom near the methoxy group harms the enhanced efficiency, which may originate from the crystallization of DBT-2F-MOP, leading to a rugged film morphology of DBT-2F-MOP, thus further affecting the crystallization of the on-top perovskite layer.

Hole‐Transporting Materials with Rational Combination of Pyridine and Dibenzo[a,c]phenazine as Electron Acceptor for Dopant‐Free Perovskite Solar Cells†

“…[ 10‐15 ] Also, they may passivate the defects and prevent moisture into perovskite layer in some cases. [ 16‐17 ] Until now, 2,2’,7,7’‐tetrakis( N , N ’‐di‐ p ‐methoxyphenylamine)‐9,9‐spirobifluorene (Spiro‐OMeTAD) is the most popular hole‐transporting material (HTM), [ 18 ] but the dependence on hydrophilic dopants may decrease the stability of PSC devices for the degradation of perovskite layer. [ 19‐20 ] Therefore, development of efficient dopant‐free HTMs is essential to improve the stability of PSCs, which requires high hole mobility and good film morphology of HTLs.…”

Structural divergence of molecular hole selective materials for viable p-i-n perovskite photovoltaics: a comprehensive review

“…Instead of an N , N -dimethyl thiophenylamine unit in DBFMT, the authors in their recent work utilized methoxyphenyl amine as terminal donor units to form DBT-MOP ( D37 ) and fluorinated methoxyphenyl in one end unit to form DBT-2F-MOP ( D38 ). 167 The introduction of a fluorine atom near the methoxy group resulted in rugged film morphology of DBT-2F-MOP which significantly affected the perovskite/HSM interface and lowered the performance compared with that of non-fluorinated DBT-MOP. For instance, DBT-MOP exhibited a better J sc /FF of 22.45 mA cm −2 /82.77% which was reduced to 19.94 mA cm −2 /75.32% upon introducing a fluorine donor unit (DBT-2F-MOP) which led to a maximum PCE of 19.5% and 15.19%, respectively.…”