Green solvent-processed efficient non-fullerene organic solar cells enabled by low-bandgap copolymer donors with EDOT side chains. Issue 2 (14th December 2018)

• Record Type: Journal Article
• Authors: Liao, Chentong; Zhang, Ming; Xu, Xiaopeng; Liu, Feng; Li, Ying; Peng, Qiang
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 2(2019)
• Page Start: 716
• Page End: 726
• Publication Date: 2018-12-14
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta10882j
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : By a combination of side chain and ternary blend strategies, novel BDT-TT-based copolymer donors were developed to improve the green solvent solubility, crystallinity, energy level, carrier mobility and blend morphology. Non-fullerene binary and ternary blend devices based on PTB-EDOTS exhibited high PCEs of 10.18% and 12.26%, respectively. Abstract : In this study, by engineering ethylenedioxythiophene (EDOT) side chains we developed two novel low-bandgap copolymers, namely, PTB-EDOT and PTB-EDOTS, for fabricating green solvent-processed but highly efficient non-fullerene organic solar cells (NF-PSCs). This molecular design strategy not only featured copolymers with excellent solubility in the green solvent 2-methyltetrahydrofuran (MeTHF) but also introduced a low-lying HOMO level, a high extinction coefficient and high crystallinity. PTB-EDOTS-based binary blend NF-PSCs exhibited a PCE of 9.28% when ITIC-Th was used as the acceptor and chlorobenzene/1-chloronaphthalene (CB/CN) as the processing solvent. When MeTHF was used instead of CB/CN, the PCE was further increased to 10.18%. To compensate for the weak absorption in the short-wavelength region and further optimize the morphology, a polymer donor (J71) with a large bandgap was added as a third component to fabricate ternary blend NF-PSCs. After the addition of 20 wt% of J71, NF-PSCs exhibited improved absorption and fine-tuned morphology. Charge transport and energy transfer were also promoted by this ternary blend strategy via an electron cascade effect, a "hole back" phenomenon and a Förster resonance energy transfer (FRET) process, which increased the maximum PCE to 12.26% with a very high fill factor (FF) of 75.6%. To the best of our knowledge, this is the best performance achieved by NF-PSCs using green solvents.