FULL PAPER www.afm-journal.de © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1808731 (1 of 9) Performance Optimization of Parallel-Like Ternary Organic Solar Cells through Simultaneous Improvement in Charge Generation and Transport Wisnu Tantyo Hadmojo, Febrian Tri Adhi Wibowo, Wooseop Lee, Hye-Kyung Jang, Yeongsik Kim, Septy Sinaga, Minsuk Park, Sang-Yong Ju, Du Yeol Ryu,* In Hwan Jung,* and Sung-Yeon Jang* Ternary organic photovoltaic (OPV) devices with multiple light-absorbing active materials have emerged as an efficient strategy for realizing further improvements in the power conversion efficiency (PCE) without building complex multijunction structures. However, the third component often acts as recombination centers and, hence, the optimization of ternary blend mor- phology poses a major challenge to improving the PCE of these devices. In this work, the performance of OPVs is enhanced through the morphological modification of nonfullerene acceptor (NFA)-containing binary active layers. This modification is achieved by incorporating fullerenes into the layers. The uniformly dispersed fullerenes are sufficiently continuous and successfully mediate the ordering of NFA without charge or energy transfer. Owing to the simultaneous improvement in the charge generation and extraction, the PCE (12.1%) of these parallel-linked ternary devices is considerably higher than those of the corresponding binary devices (9.95% and 7.78%). Moreover, the additional energy loss of the ternary device is minimized, compared with that of the NFA-based binary device, due to the judicious control of the effective donor:acceptor composition of the ternary blends. DOI: 10.1002/adfm.201808731 W. T. Hadmojo, F. T. A. Wibowo, S. Sinaga, Prof. I. H. Jung, Prof. S.-Y. Jang Department of Chemistry Kookmin University 77 Jeongneung-ro, Seongbuk-gu, Seoul 02707, Republic of Korea E-mail: ihjung@kookmin.ac.kr; syjang@kookmin.ac.kr W. Lee, H.-K. Jang, Y. Kim, Prof. D. Y. Ryu Department of Chemical and Biomolecular Engineering Yonsei University 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea E-mail: dyryu@yonsei.ac.kr M. Park, Prof. S.-Y. Ju Department of Chemistry Yonsei University 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201808731. effectively extended the light utilization of organic photovoltaic (OPV) devices. [1–3] In particular, due to the photon-to-current conversion up to the near-infrared (NIR) region, a power conversion efficiency (PCE) of 9–12% has been achieved for the OPV devices using indacenodithio- phene-based small molecule NFAs such as ITIC. [4–7] However, the morphological characteristics of NFA-based bulk het- erojunction (BHJ) active films differ from those of conventional fullerene-based BHJ films. The corresponding suboptimal charge generation and transport have often resulted in NFA-based BHJ active layers. Efficient morphological manipula- tion of these layers may provide the oppor- tunity for further improvement in the performance of these devices. Construction of ternary BHJ layers with multiple light-absorbing active mate- rials has emerged as an efficient strategy for improving the PCE of OPV devices without building complex multijunction structures (i.e., tandem devices). [8–13] The choice of the third component with appro- priate energy levels and complementary absorption is crucial for optimizing the current density (J SC ) and open-circuit voltage (V OC ) of the devices. [14–19] However, the effect of this compo- nent on the morphology (as manifested through the occurrence of recombination centers) may be unfavorable for charge gener- ation and/or charge transport. [20–22] Optimization of the ternary blend (including NFA) morphology for maximum charge gen- eration/transport and minimum energy loss represents a major challenge to the improvement of PCE devices. The use of fullerenes as the third component for the NFA- containing BHJ blends has often improved the device perfor- mance due to the enhanced visible absorption by the fullerenes or the charge cascading effects from NFAs to these fuller- enes. [10,23,24] While some fullerenes exhibited efficient absorp- tion at ≈400–500 nm, the charge transfer from higher-lying lowest unoccupied molecular orbital (LUMO) levels of NFAs to lower-lying LUMO levels of fullerenes enhanced electron transport. [23] However, the mismatch of the LUMO levels of the fullerenes and NFA increased the energy loss of the devices Ternary Organic Solar Cells 1. Introduction Recent development in low-bandgap organic nonfullerene acceptors (NFAs) and high-bandgap donor polymers has Adv. Funct. Mater. 2019, 1808731