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Enhancing the efficiency of PTB7-Th:CO i 8DFIC-based ternary solar cells with versatile third components

DOI: 10.1063/1.5125438 DOI Help

Authors: Wei Li (Wuhan University of Technology) , Zuo Xiao (Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing) , Joel As. Smith (University of Sheffield) , Jinlong Cai (Wuhan University of Technology) , Donghui Li (Wuhan University of Technology) , Rachel C. Kilbride (University of Sheffield) , Emma L. K. Spooner (University of Sheffield) , Onkar S. Game (University of Sheffield) , Xianyi Meng (Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing) , Dan Liu (Wuhan University of Technology) , Richard A. L. Jones (University of Sheffield) , David G. Lidzey (University of Sheffield) , Liming Ding (Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing) , Tao Wang (Wuhan University of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Physics Reviews , VOL 6

State: Published (Approved)
Published: December 2019
Diamond Proposal Number(s): 20419

Abstract: Traditional single-junction binary organic solar cells suffer from narrow absorption windows, limiting their ability to harvest photons. One promising approach to avoid this issue is through the construction of a ternary system to enhance the spectral response and efficiency. However, the complex morphology and photophysical processes within ternary blends leave the criteria of an effective third component unclear, and so they remain a challenge. In this work, we report on the fabrication of PTB7-Th:COi8DFIC-based ternary solar cells with enhanced efficiency by employing either a polymer donor or a nonfullerene acceptor as the third component. We demonstrate that the third component is highly associated with the condensed state of the host acceptor and is the primary factor in determining efficiency improvement. The π-π stacking molecular packing of COi8DFIC helps to maintain the optimal phase separation within the ternary blends and improves both the hole and electron charge mobilities, resulting in enhanced power conversion efficiency of over 14%, compared to 13.1% in binary devices. We also found an excessive amount of polymer donor or nonfullerene acceptor increases the phase separation and encourages lamellar crystallization with the host acceptor domain, resulting in reduced light-harvesting and external quantum efficiencies at long wavelengths. Our results provide a rational guide to selecting the third component to fabricate high-performance nonfullerene-based ternary solar cells.

Journal Keywords: Solar cells; Electronic transport; Quantum efficiency; Transmission electron microscopy; Absorption spectroscopy; Photovoltaics; Excitons; Morphology studies

Subject Areas: Materials, Physics, Energy


Instruments: I07-Surface & interface diffraction