Fine-Tuning Energy Levels via Asymmetric End Groups Enables Polymer Solar Cells with Efficiencies over 17%

Luo, Zhenghui; Ma, Ruijie; Liu, Tao; Yu, Jianwei; Xiao, Yiqun; Sun, Rui; Xie, Guanshui; Yuan, Jun; Chen, Yuzhong; Chen, Kai; Chai, Gaoda; Sun, Huiliang; Min, Jie; Zhang, Jian; Zou, Yingping; Yang, Chuluo; Lu, Xinhui; Gao, Feng; Yan, He

doi:10.1016/j.joule.2020.03.023

Cited by 376 publications

(278 citation statements)

References 63 publications

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“…[ 1–6 ] Nonfullerene small molecular acceptors (SMAs) [ 7–29 ] are the main driving force for the recent development of the field, with power conversion efficiencies (PCEs) over 17% reported by different teams. [ 30–43 ] SMAs have many attractive properties including their strong and tunable absorption, the easily adjustable energy levels and the enhanced chemical and device stability. Most of these excellent features are enabled by the flexible and feasible synthesis of the SMAs that leads to numerous judiciously designed molecular structures.…”

Section: Methodsmentioning

confidence: 99%

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

et al. 2020

Solar RRL

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A multitude of studies have been conducted on organic solar cells (OSCs) to understand how end group halogenation changes the property of the small molecular acceptors (SMAs) energetically, morphologically, and so on. But how the halogenation impacts the miscibility between SMAs and polymers, which is an important index to thermodynamically predict and understand the morphology of blend films, has not been systematically studied, particularly for the state‐of‐the‐art polymer–SMA blends. Herein, three series of asymmetric or symmetric SMAs, all reported recently with high photovoltaic performances, are used to investigate the effect of halogenation on miscibility, crystallinity, and solar cell performance. Using the asymmetric SMA named TPIC, and its derivatives (TPIC‐4F and TPIC‐4Cl) as the focus, it is revealed that the enhancement in solar cell performance for the halogenated SMAs is to reduce the miscibility between the acceptor and donor, which leads to a more favorable morphology, enhanced charge transport, and an extended absorption range. Similarly, the halogenation‐induced reduction in miscibility for the initially overmixed donor:acceptor blend is also demonstrated in the symmetric ITIC and the state‐of‐the‐art BTP series, where attractive power conversion efficiencies (PCEs) of 16.5% and 16.8%, respectively, are achieved by the halogenated‐SMA‐based devices in each series.

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Section: Methodsmentioning

confidence: 99%

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

et al. 2020

Solar RRL

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“…[31,62,[65][66][67] Typically, halogen atoms (fluorine and chlorine) are introduced to the end group. [36,62,66,67] For example, Hou and coworkers attached fluorine atoms onto the end group of IEICO and developed IEICO-4F with a narrow bandgap of 1.24 eV. [62] Its absorption spectrum shows a redshift of approximately 75 nm compared with the original compound, IEICO.…”

Section: Absorption Expansion For Enhanced Photon Utilizationmentioning

confidence: 99%

Emerging Approaches in Enhancing the Efficiency and Stability in Non‐Fullerene Organic Solar Cells

Zhao

Zhang

et al. 2020

Advanced Energy Materials

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the center, side-chains hanging out from the molecular plane, and two strong compact electron-withdrawing end groups. Independent modifications of these three parts provide diverse NFA molecular structures, thus enabling strong absorption in the visible and/or near infrared (NIR) regions, easily tunable energy levels, and finely tunable crystallinity. [28-32] In addition, low voltage losses are a significant feature of NFA OSCs compared to their fullerene counterparts, contributing to the rapidly increasing PCE. [33-36] At the same time, the operational stability of NFA OSCs has also been demonstrated to be promising, [37-41] although further improvement is required to meet the standard for practical applications. Along with the rapid development of materials and devices, the fundamental understanding of OSCs is also moving forward, though at a slower pace compared with that of material development and device engineering. One of the greatest impediments to developing a fundamental understanding of OSCs lies in the bulk heterojunction (BHJ) structure. The invention of BHJ, which is a milestone in OSC research, increases the interfacial area between the electron donor and electron acceptor materials, overcoming the issues of short exciton diffusion length, limited exciton lifetime, and charge separation that limits bilayer junctions. [42] Together with these advantages, the BHJ structure also presents challenges. The multiple phases and complex interfaces bring about sophisticated hierarchical morphologies and complicated charge dynamics, which are difficult for experimental observation and control. In NFA-based systems, some of these challenges have even been manifested. The similarity in the element constitution makes it difficult to spatially distinguish the electron donor and electron acceptor materials. Additionally, the resemblance of energy makes the spectra indistinguishable for charge-transfer (CT) states and singlet excitons. [33] Furthermore, OSC materials are updated so fast that the new materials can be distinct from previous ones, and the characteristics may be entirely different. This review covers emerging approaches for enhancing the efficiency and stability of non-fullerene OSCs. We highlight that recent advances on non-fullerene OSCs result from the coordinated development of donors and acceptors; those who are interested in a comprehensive understanding of donor materials are referred to recent review articles on this topic. [43-49] In this review, we mainly focus on the development of acceptors. We summarize new strategies for high short-circuit current (J SC) and fill factor (FF). A variety of methods, for example, extended absorption and effective morphology control, are discussed. We also introduce design rules for low energy losses, especially by The past three years have witnessed rapid growth in the field of organic solar cells (OSCs) based on non-fullerene acceptors (NFAs), with intensive efforts being devoted to material development, device engineering, and understanding of device physi...

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“…[ 34–40 ] Among a myriad of NFAs, rylene imides/amides and acceptor–donor–acceptor (A–D–A) type acceptors are the most important classes and exhibit promising performance in current researches. [ 41–51 ] To date, OSCs have yielded power conversion efficiencies (PCE) over 11% [ 52 ] for PDI‐based devices and over 17% [ 53–63 ] for A–D–A‐type SMA‐based devices, even OSCs with efficiencies over 18% have been realized. [ 58 ]…”

Section: Introductionmentioning

confidence: 99%

Isomerization Strategy of Nonfullerene Small‐Molecule Acceptors for Organic Solar Cells

Luo

Liu

Yan

et al. 2020

Adv Funct Materials

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Nonfullerene acceptors (NFAs) are a current focus of research on bulkheterojunction organic solar cells (OSCs), as they can exhibit strong absorption, suitably matched energy levels, and good stability. Isomerization affords a new material design strategy for nonfullerene small-molecule acceptors (SMAs). In this article, the development of isomeric nonfullerene SMAs, including isomeric perylene diimide (PDI)-based nonfullerene SMAs and isomeric acceptor-donor-acceptor (A-D-A)-type nonfullerene SMAs, is reviewed. The general design principles for isomeric SMAs and the key structure-property relationships are comprehensively surveyed and discussed. The remaining challenges and promising future directions of isomeric nonfullerene acceptors are presented.

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Fine-Tuning Energy Levels via Asymmetric End Groups Enables Polymer Solar Cells with Efficiencies over 17%

Abstract: Asymmetric acceptor BTP-2F-ThCl-based devices gave the best PCE of 17.06% due to the optimal energy levels relative to those of the devices based on their symmetrical counterparts, BTP-4F (16.37%) and BTP-2ThCl (14.49%).

Cited by 376 publications

References 63 publications

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

Emerging Approaches in Enhancing the Efficiency and Stability in Non‐Fullerene Organic Solar Cells

Isomerization Strategy of Nonfullerene Small‐Molecule Acceptors for Organic Solar Cells

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