Abstract
We introduce two novel solution-processable electron acceptors based on an isomeric core of the much explored diketopyrrolopyrrole (DPP) moiety, namely pyrrolo[3,2-b]pyrrole-1,4-dione (IsoDPP). The newly designed and synthesized compounds, 6,6′-[(1,4-bis{4-decylphenyl}-2,5-dioxo-1,2,4,5-tetrahydropyrrolo[3,2-b]pyrrole-3,6-diyl)bis(thiophene-5,2-diyl)]bis[2-(2-butyloctyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione] (NAI-IsoDPP-NAI) and 5,5′-[(1,4-bis{4-decylphenyl}-2,5-dioxo-1,2,4,5-tetrahydropyrrolo[3,2-b]pyrrole-3,6-diyl)bis(thiophene-5,2-diyl)]bis[2-(2-butyloctyl)isoindoline-1,3-dione] (PI-IsoDPP-PI) have been synthesized via Suzuki couplings using IsoDPP as a central building block and napthalimide or phthalimide as end-capping groups. The materials both exhibit good solubility in a wide range of organic solvents including chloroform (CF), dichloromethane (DCM), and tetrahydrofuran (THF), and have a high thermal stability. The new materials absorb in the wavelength range of 300–600 nm and both compounds have similar electron affinities, with the electron affinities that are compatible with their use as acceptors in donor-acceptor bulk heterojunction (BHJ) organic solar cells. BHJ devices comprising the NAI-IsoDPP-NAI acceptor with poly(3-n-hexylthiophene) (P3HT) as the donor were found to have a better performance than the PI-IsoDPP-PI containing cells, with the best device having a VOC of 0.92 V, a JSC of 1.7 mAcm−2, a FF of 63%, and a PCE of 0.97%.
Highlights
Organic solar cells (OSCs) which are fabricated using solution processing techniques have been considered to be a revolutionary technology for harvesting solar energy and converting it into electrical energy due to their outstanding advantages including low cost, short economic and energy pay-back times, the possibility of using simple manufacturing processes, their light-weight nature, and the capacity for fabrication on flexible substrates for large-area devices [1,2,3]
New Non-Fullerene Acceptor Molecular Design and Synthesis and PI-IsoDPP-PI are depicted in Scheme 1
Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements were performed to evaluate the thermal properties of the electron accepting materials
Summary
Organic solar cells (OSCs) which are fabricated using solution processing techniques have been considered to be a revolutionary technology for harvesting solar energy and converting it into electrical energy due to their outstanding advantages including low cost, short economic and energy pay-back times, the possibility of using simple manufacturing processes, their light-weight nature, and the capacity for fabrication on flexible substrates for large-area devices [1,2,3]. The outstanding chemical properties of diketopyrrolopyrrole (DPP) moiety such as strong electron-withdrawing ability, high polarity, high charge carrier mobility, strong intermolecular interactions, and good solubility, have led it to be used for constructing various donor-acceptor-based non-polymeric materials and polymers. These DPP-based conjugated materials have been widely employed for a number of optoelectronic devices such as transistors (p-type, n-type, and ambipolar), solar cells, logic circuits, sensors, memory devices, and photodetectors [13,14,15,16,17,18].
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