Near‐Infrared‐Absorbing and Dopant‐Free Heterocyclic Quinoid‐Based Hole‐Transporting Materials for Efficient Perovskite Solar Cells

Abstract

New heterocyclic quinoid-based hole transporting materials (HTMs) with a rigid quinoid core [3,6-di(2H-imidazol-2-ylidene)cyclohexa-1,4-diene] have been synthesized. The new HTMs have good hole mobility (>10 cm V s ) and very intense absorption in the near-infrared region extending to >800 nm. High performance perovskite solar cells can be fabricated using these HTMs without dopant. The best cell efficiency under simulated AM 1.5 G illumination reaches 12.22 %, which is comparable with that (12.58 %) using doped 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD) as the HTM.

Dopant‐Free Hole Transporting Materials for Perovskite Solar Cells

“…However, using dopants has improved the efficiency up to 12.3%. Maximum efficiency of 12.22% has been achieved for perovskite devices using a dopant‐free HTM with rigid quinoid core, DIQ‐C12 ( 138 ) . Fabricated in same conditions, devices using doped spiro‐OMeTAD exhibited a comparable PCE of 12.6%.…”

Recent Progress on the Long‐Term Stability of Perovskite Solar Cells

“…However, Li‐TFSI has aggravated the degradation of PVSCs due to its hygroscopic nature and the additional doping materials . Recently, doping‐free HTLs are fabricated with the high performance and good stability, such as tetrathiafulvalene derivative (TTF‐1), SAF‐OMe, 3,6‐di(2H‐imidazol‐2‐ylidene)cyclohexa‐1,4‐diene derivatives (DIQ‐C6 and DIQ‐C12), BTPA‐TCNE, etc. Chen and co‐workers present a new structural design of hole‐transporting material, Trux‐OMeTAD, which was designed by introducing triarylamine and aliphatic side chains onto the C 3h Truxene core with high mobility and suitable surface energy.…”

Quinoidal 2,2′,6,6′‐Tetraphenyl‐Dipyranylidene as a Dopant‐Free Hole‐Transport Material for Stable and Cost‐Effective Perovskite Solar Cells

“…Finally,P SCs based on DIPO-Ph 4 possess as uperior stability compared to doped-spiro-OMeTAD-based devices when tested over 600 h. dal small planar molecules were also reported as HTMs in PSCs,n amely alkylatedt etrathiafulvalene (TTF) derivatives (PCE = 11.03 %), [28 ]a nd 3,6-di(2H-imidazol-2-ylidene)cyclohexa-1,4-diene (PCE = 11.6 %). [29] Aw idespreads trategy to improve charge transport in HTMs consists of addingd opants of various types such as lithium bis(trifluoro-methanesulfonyl)imide( Li-TFSI), tertbutylpyridine (t-BP) and tris[2-(1H-pyrazol-1-yl)pyridine]cobalt(III)( FK 102). [30][31][32] However,t hese dopants are hydrophilic, which compromises solar cell stability,c onsidering that the perovskite active layers are susceptible to moistureinduced degradation.…”

“…Recently, Zou and co‐workers reported the use of rubrene in a planar‐inverted‐configuration PSC device with a PCE as high as 15.83 % . In addition, two types of quinoidal small planar molecules were also reported as HTMs in PSCs, namely alkylated tetrathiafulvalene (TTF) derivatives (PCE=11.03 %), [28 ] and 3,6‐di(2 H ‐imidazol‐2‐ylidene)cyclohexa‐1,4‐diene (PCE=11.6 %) …”