Premium
Tailor‐Made Hole‐Conducting Coadsorbents for Highly Efficient Organic Dye‐Sensitized Solar Cells
Author(s) -
Choi In Taek,
Ju Myung Jong,
Song Sang Hyun,
Kim Sang Gyun,
Cho Dae Won,
Im Chan,
Kim Hwan Kyu
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201301658
Subject(s) - dye sensitized solar cell , energy conversion efficiency , electrolyte , stacking , cascade , materials science , biphenyl , photochemistry , chemistry , optoelectronics , organic chemistry , chromatography , electrode
The Y‐shaped, low molecular mass, hole‐conductor (HC), acidic coadsorbents 4‐{3,7‐bis[4‐(2‐ethylhexyloxy)phenyl]‐10 H ‐phenothiazin‐10‐yl}benzoic acid ( PTZ1 ) and 4‐{3,7‐bis[4‐(2‐ethylhexyloxy)phenyl]‐10 H ‐phenothiazin‐10‐yl}biphenyl‐4‐carboxylic acid ( PTZ2 ) were developed. Owing to their tuned and negative‐shifted HOMO levels (vs. NHE), they were used as HC coadsorbents in dye‐sensitized solar cells (DSSCs) to improve cell performance through desired cascade‐type hole‐transfer processes. Their detailed functions as HC coadsorbents in DSSCs were investigated to obtain evidence for the desired cascade‐type hole‐transfer processes. They have multiple functions, such as preventing π–π stacking of dye molecules, harvesting light of shorter wavelengths, and faster dye regeneration. By using PTZ2 as the tailor‐made HC coadsorbent on the TiO 2 surface with the organic dye NKX2677, an extremely high conversion efficiency of 8.95 % was achieved under 100 mW cm −2 AM 1.5G simulated light (short‐circuit current J SC =16.56 mA cm −2 , open‐circuit voltage V OC =740 mV, and fill factor of 73 %). Moreover, J SC was increased by 13 %, V OC by 27 % and power‐conversion efficiency by 49 % in comparison to an NKX2677‐based DSSC without an HC coadsorbent. This is due to the HC coadsorbent having a HOMO energy level well matched to that of the NKX‐2677 dye to induce the desired cascade‐type hole‐transfer processes, which are associated with a slower charge recombination, fast dye regeneration, effective screening of liquid electrolytes, and an induced negative shift of the quasi‐Fermi level of the electrode. Thus, this new class of Y‐shaped, low molecular weight, organic, HC coadsorbents based on phenothiazine carboxylic acid derivatives hold promise for highly efficient organic DSSCs.