Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel Harvesting near- and far-field plasmonic enhancements from large size gold nanoparticles for improved performance in organic bulk heterojunction solar cells Jongmoon Shin a,1 , Myungkwan Song a,**,1 , Hassan Hafeez b,1 , P. Justin Jeusraj b,1 , Dong Hyun Kim b , Jong Chan Lee b , Won Ho Lee b , Dae Keun Choi b , Chul Hoon Kim c,*** , Tae-Sung Bae d , Seung Min Yu d , Kyoung-Ho Kim e , Hong-Gyu Park f , Kwun-Bum Chung g , Aeran Song g , Yong-Cheol Kang h , Juuyn Park h , Chang Su Kim a , Seung Yoon Ryu b,* a Surface Technology Division, Korea Institute of Materials Science (KIMS), 797 Changwondaero, Sungsan-Gu, Changwon, Gyeongnam, 642-831, Republic of Korea b School of Display and Semiconductor Physics, College of Science and Technology, Korea University, Sejong Campus 2511, Sejong-ro, Sejong City, 339-770, Republic of Korea c Department of Advanced Materials Chemistry, College of Science and Technology, Korea University, Sejong Campus 2511, Sejong-ro, Sejong City, 339-770, Republic of Korea d Jeonju Center, Korea Basic Science Institute (KBSI), Analysis & Researcher Division, 634-18 Geumam-dong, Deokjin-gu, Jeonju-si, Jeollabuk-do, 561-756, Republic of Korea e Department of Physics, Chungbuk National University, Cheongju, 28644, Republic of Korea f Department of Physics, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 136-701, Republic of Korea g Division of Physics and Semiconductor Science, Dongguk University, Seoul, 04620, Republic of Korea h Department of Chemistry, Pukyong National University, 45 Yongso-Ro, Nam-gu, Busan, 48513, Republic of Korea ARTICLE INFO Keywords: Organic solar cells Gold nanoparticles Bulk heterojunction Near-field plasmon resonance Far-field scattering Time resolved photoluminescence ABSTRACT The high stability and strong coupling nature of gold nanoparticles (Au-NPs) than other metal counter parts have attracted the solar cell industry to pursue enhanced performances. Herein, we report on the improved perfor- mance of polymer bulk hetero-junction (BHJ) solar cells by the incorporation of large-size Au-NPs in the hole transport layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). To examine the re- producibility of the enhancement parameters, two different donor photoactive materials have been adapted and the role of larger-size (> 70 nm, i.e. 71, 80, 87, 103 nm) Au-NPs in BHJ solar cells have been studied extensively. Significantly, when employing Au-NPs smaller than 80 nm, near-field coupling (localized surface plasmon re- sonance; LSPR) was prevalent, while the infusion of Au-NPs with sizes greater than 87 nm resulted in far-field scattering enhancement as the dominant effect, which was clearly determined using time resolved photo lu- minescence studies. The superior power conversion efficiency of 5.35% and 8.58% was achieved with PBDTTT- C: PC 61 BM and PTB7: PC 71 BM BHJs respectively, by employing 87 nm Au-NPs due to the balanced contribution of near- and far-field plasmonic effects, improved vertical coverage and better interfacial properties. This study illustrates that 87 nm Au-NPs is the maximum size to attain the improved efficiency, above which the rate of enhancement reduces dramatically. https://doi.org/10.1016/j.orgel.2018.12.024 Received 20 August 2018; Received in revised form 6 November 2018; Accepted 15 December 2018 * Corresponding author. School of Display and Semiconductor Physics, College of Science and Technology, Korea University, Sejong Campus 2511, Sejong-ro, Sejong City, 30019, Republic of Korea. ** Corresponding author. Surface Technology Division, Korea Institute of Materials Science (KIMS), 797 Changwondaero, Sungsan-Gu, Changwon, Gyeongnam, 642-831, Republic of Korea. *** Corresponding author. Department of Advanced Materials Chemistry, College of Science and Technology, Korea University, Sejong Campus 2511, Sejong-ro, Sejong City, 339-770, Republic of Korea. E-mail addresses: smk1017@kims.re.kr (M. Song), chulhoon@korea.ac.kr (C.H. Kim), justie74@korea.ac.kr (S.Y. Ryu). 1 These authors equally contributed to this paper. Organic Electronics 66 (2019) 94–101 Available online 17 December 2018 1566-1199/ © 2018 Elsevier B.V. All rights reserved. T