Novel Carbazole-Based Hole-Transporting Materials with Star-Shaped Chemical Structures for Perovskite-Sensitized Solar Cells

Abstract

Novel carbazole-based hole-transporting materials (HTMs), including extended π-conjugated central core units such as 1,4-phenyl, 4,4'-biphenyl, or 1,3,5-trisphenylbenzene for promoting effective π-π stacking as well as the hexyloxy flexible group for enhancing solubility in organic solvent, have been synthesized as HTM of perovskite-sensitized solar cells. A HTM with 1,3,5-trisphenylbenzene core, coded as SGT-411, exhibited the highest charge conductivity caused by its intrinsic property to form crystallized structure. The perovskite-sensitized solar cells with SGT-411 exhibited the highest PCE of 13.00%, which is 94% of that of the device derived from spiro-OMeTAD (13.76%). Time-resolved photoluminescence spectra indicate that SGT-411 shows the shortest decay time constant, which is in agreement with the trends of conductivity data, indicating it having fastest charge regeneration. In this regard, a carbazole-based HTM with star-shaped chemical structure is considered to be a promising candidate HTM.

Facilely Synthesized spiro[fluorene‐9,9′‐phenanthren‐10′‐one] in Donor–Acceptor–Donor Hole‐Transporting Materials for Perovskite Solar Cells

“…Recently,o rganic-inorganic halide perovskite solar cells (PSCs) have attracted considerable attention because of their outstanding performance in converting sunlight to electricity at al ow cost compared with silicon-based photovoltaict echnology.T he first PSCs, as ana-lyzed by Miyasaka in 2009, had power conversion efficiency (PCE) of 3.8 %. [12][13][14] To overcome these issues, numerouss tudies have focusedo nl ow-costp roduction without as piro-based linkage in the HTM, mainly using acene, [15] carbazole, [16][17][18][19][20][21][22][23] indole, [24][25][26] phenothiazine, [27] phenoxazine, [28] thiophene, [29][30][31][32][33][34][35] triarylamine, [36][37][38][39] triazateuxene, [40][41][42][43] and truxene. [11] In the conventional devicec onfiguration, 2,2',7,7'-tetrakis[N,N-di(4methoxyphenyl)amino]-9,9'-spirobifluorene( Spiro-OMeTAD) is generally used as the hole-transporting material( HTM) and has demonstrated PCEs of 20-21 %i nP SCs.…”

π-Conjugated Materials as the Hole-Transporting Layer in Perovskite Solar Cells

“…One of the strategies is finally to exploit small molecules with a carbazole-based arm linked together by a core moiety [28]. To these carbazole arms were added flexible hexyloxy groups to enhance the solubility of the molecule in chlorobenzene, which is often used as solvent for the Spiro-OMeTAD.…”

Low‐Cost Carbazole‐Based Hole‐Transport Material for Highly Efficient Perovskite Solar Cells

“…[15][16][17][18] Liu et al reporteds piro[fluorene-9,9'-xanthene]-basedH TMs for PSCs, in which not only ah igh PCE but also improved stabilityw ere achieved. [23][24][25][26][27][28][29][30][31][32] In the molecular structures of many HTMs, ac arbazole moiety together with some atypical hole-transport groupsf orm the core of the molecule and a phenylamine structure are found on the outsideo ft he molecule core. However,t hese materials and Spiro-OMeTAD all contain fluoride groups, which are responsible for al arge proportion of the final cost of the ultimate product.…”

“…[19] Xu et al [20] and Bi et al [21] achieved high PCEs of over 19 % using similarly structured small-molecule materials (X59 and X60). [23,24,[26][27][28][29] These atypical hole-transportg roups( e.g., benzene and biphenyl) can transport both holes and electrons, which mayi mpair the hole mobility of theseHTMs. The replacement of fluorine with al ess expensive substitute seems to be an effective way to cut the cost of the HTMs.…”