18.4 % Organic Solar Cells Using a High Ionization Energy Self-Assembled Monolayer as Hole-Extraction Interlayer

Yuanbao Lin; Artiom Magomedov; Yuliar Firdaus; Dimitris Kaltsas; Abdulrahman El-Labban; Hendrik Faber; Dipti R Naphade; Emre Yengel; Xiaopeng Zheng; Emre Yarali; Neha Chaturvedi; Kalaivanan Loganathan; Despoina Gkeka; Sanaa H AlShammari; Osman M Bakr; Frédéric Laquai; Leonidas Tsetseris; Vytautas Getautis; Thomas D Anthopoulos

doi:10.1002/cssc.202100707

18.4 % Organic Solar Cells Using a High Ionization Energy Self-Assembled Monolayer as Hole-Extraction Interlayer

ChemSusChem. 2021 Sep 6;14(17):3569-3578. doi: 10.1002/cssc.202100707. Epub 2021 May 17.

Authors

Yuanbao Lin¹, Artiom Magomedov², Yuliar Firdaus^{1

3}, Dimitris Kaltsas⁴, Abdulrahman El-Labban¹, Hendrik Faber¹, Dipti R Naphade¹, Emre Yengel¹, Xiaopeng Zheng⁵, Emre Yarali¹, Neha Chaturvedi¹, Kalaivanan Loganathan¹, Despoina Gkeka¹, Sanaa H AlShammari¹, Osman M Bakr⁵, Frédéric Laquai¹, Leonidas Tsetseris⁴, Vytautas Getautis², Thomas D Anthopoulos¹

Affiliations

¹ King Abdullah University of Science and Technology (KAUST), KAUST Solar Center (KSC), 23955, Thuwal, Saudi Arabia.
² Department of Organic Chemistry, Kaunas University of Technology, LT-50254, Kaunas, Lithuania.
³ Research Center for Electronics and Telecommunication, Indonesian Institute of Science, Jalan Sangkuriang Komplek LIPI Building 20 level 4, 40135, Bandung, Indonesia.
⁴ Department of Physics, National Technical University of Athens, GR-15780, Athens, Greece.
⁵ King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Division (PSE), 23955, Thuwal, Saudi Arabia.

PMID: 33928763
DOI: 10.1002/cssc.202100707

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.

Keywords: hole-extraction interlayer; organic solar cells; photovoltaics; power conversion efficiency; self-assembled monolayer.

Abstract

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