1. 18.4 % Organic Solar Cells Using a High Ionization Energy Self‐Assembled Monolayer as Hole‐Extraction Interlayer
- Author
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Osman M. Bakr, Xiaopeng Zheng, Dimitris Kaltsas, Leonidas Tsetseris, Hendrik Faber, Yuliar Firdaus, Artiom Magomedov, Yuanbao Lin, Neha Chaturvedi, Thomas D. Anthopoulos, Abdulrahman El-Labban, Kalaivanan Loganathan, Frédéric Laquai, Dipti R Naphade, Emre Yarali, Sanaa Hayel Nazil Alshammari, Despoina Gkeka, Emre Yengel, and Vytautas Getautis
- Subjects
Materials science ,Organic solar cell ,General Chemical Engineering ,Energy conversion efficiency ,Self-assembled monolayer ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Styrene ,chemistry.chemical_compound ,General Energy ,Sulfonate ,PEDOT:PSS ,chemistry ,Monolayer ,Environmental Chemistry ,Physical chemistry ,General Materials Science ,0210 nano-technology ,HOMO/LUMO - Abstract
Self-assembled monolayers (SAMs) based on Br-2PACz ([2-(3,6-dibromo-9H-carbazol-9-yl)ethyl]phosphonic acid) 2PACz ([2-(9H-Carbazol-9-yl)ethyl]phosphonic acid) and MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) molecules were investigated as hole-extracting interlayers in organic photovoltaics (OPVs). The highest occupied molecular orbital (HOMO) energies of these SAMs were measured at -6.01 and -5.30 eV for Br-2PACz and MeO-2PACz, respectively, and found to induce significant changes in the work function (WF) of indium-tin-oxide (ITO) electrodes upon chemical functionalization. OPV cells based on PM6 (poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)]) : BTP-eC9 : PC71 BM ([6,6]-phenyl-C71-butyric acid methyl ester) using ITO/Br-2PACz anodes exhibited a maximum power conversion efficiency (PCE) of 18.4 %, outperforming devices with ITO/MeO-2PACz (14.5 %) and ITO/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT : PSS) (17.5 %). The higher PCE was found to originate from the much higher WF of ITO/Br-2PACz (-5.81 eV) compared to ITO/MeO-2PACz (4.58 eV) and ITO/PEDOT : PSS (4.9 eV), resulting in lower interface resistance, improved hole transport/extraction, lower trap-assisted recombination, and longer carrier lifetimes. Importantly, the ITO/Br-2PACz electrode was chemically stable, and after removal of the SAM it could be recycled and reused to construct fresh OPVs with equally impressive performance.
- Published
- 2021