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Work Function Control of Interfacial Buffer Layers for Efficient and Air‐Stable Inverted Low‐Bandgap Organic Photovoltaics
Author(s) -
Worfolk Brian J.,
Hauger Tate C.,
Harris Kenneth D.,
Rider David A.,
Fordyce Jordan A. M.,
Beaupré Serge,
Leclerc Mario,
Buriak Jillian M.
Publication year - 2012
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201100714
Subject(s) - materials science , pedot:pss , photoactive layer , work function , organic solar cell , polythiophene , polymer solar cell , acceptor , indium tin oxide , band gap , chemical engineering , energy conversion efficiency , thiophene , homo/lumo , active layer , polymer , conductive polymer , layer (electronics) , nanotechnology , optoelectronics , organic chemistry , composite material , thin film transistor , chemistry , physics , condensed matter physics , molecule , engineering
A water‐soluble cationic polythiophene derivative, poly[3‐(6‐{4‐ tert ‐butylpyridiniumyl}‐hexyl)thiophene‐2,5‐diyl] [P3(TBP)HT], is combined with anionic poly(3,4‐ethylenedioxythiophene):poly( p ‐styrenesulfonate) (PEDOT:PSS) on indium tin oxide (ITO) substrates via electrostatic layer‐by‐layer (eLbL) assembly. By varying the number of eLbL layers, the electrode's work function is precisely controlled from 4.6 to 3.8 eV. These polymeric coatings are used as cathodic interfacial modifiers for inverted‐mode organic photovoltaics that incorporate a photoactive layer composed of either poly[(3‐hexylthiophene)‐2,5‐diyl] (P3HT) and the fullerene acceptor [6,6‐phenyl‐C 61 ‐butyric acid methyl ester (PC 61 BM) or the low bandgap polymer [poly({4,8‐di(2‐ethylhexyloxyl)benzo[1,2‐b:4,5‐b′]dithiophene}‐2,6‐diyl)‐alt‐({5‐octylthieno[3,4‐c]pyrrole‐4,6‐dione}‐1,3‐diyl) (PBDTTPD)] and the electron acceptor [6,6‐phenyl‐C 71 ‐butyric acid methyl ester (PC 71 BM)]. The power conversion efficiency (PCE) of the resulting photovoltaic device is dependent on the composition of the eLbL‐assembled interface and permits the fabrication of devices with efficiencies of 3.8% and 5.6% for P3HT and PBDTTPD donor polymers, respectively. Notably, these devices demonstrate significant stability with a P3HT:PC 61 BM system maintaining 83% of its original PCE after 1 year of storage and a PBDTTPD:PC 71 BM system maintaining 97% of its original PCE after over 1000 h of storage in air, according to the ISOS‐D‐1 shelf protocol.