Synthesis of 5H-Dithieno[3,2-b:2′,3′-d]pyran as an Electron-Rich Building Block for Donor–Acceptor Type Low-Bandgap Polymers

Abstract

We describe the detailed synthesis and characterization of an electron-rich building block, dithienopyran (DTP), and its application as a donor unit in lowbandgap conjugated polymers. The electron-donating property of the DTP unit was found to be the strongest among the most frequently used donor units such as benzodithiophene (BDT) or cyclopentadithiophene (CPDT) units. When the DTP unit was polymerized with the strongly electron-deficient difluorobenzothiadiazole (DFBT) unit, a regiorandom polymer (PDTP−DFBT, bandgap = 1.38 eV) was obtained. For comparison with the DTP unit, polymers containing alternating benzodithiophene (BDT) or cyclopentadithiophene (CPDT) units and the DFBT unit were synthesized (PBDT−DFBT and PCPDT−DFBT). We found that the DTP based polymer PDTP−DFBT shows significantly improved solubility and processability compared to the BDT or CPDT based polymers. Consequently, very high molecular weight and soluble PDTP−DFBT can be obtained with less bulky side chains. Interestingly, PDTP−DFBT shows excellent performance in bulk-heterojunction solar cells with power conversion efficiencies reaching 8.0%, which is significantly higher than PBDT−DFBT and PCPDT−DFBT based devices. This study demonstrates that DTP is a promising building block for high-performance solar cell materials.

Electroactive and Photoactive Poly[Isoindigo-alt-EDOT] Synthesized Using Direct (Hetero)Arylation Polymerization in Batch and in Continuous Flow

“…This reduction in photocurrent generation is commonly reported for lower molecular weights materials. 30,32,33 AFM studies of the active layers show very similar morphology organization between all samples using the DIO additive, regardless of the molecular weights tested. This could explain the similarity of the V oc and the FF between all samples.…”

Elucidating Double Aggregation Mechanisms in the Morphology Optimization of Diketopyrrolopyrrole‐Based Narrow Bandgap Polymer Solar Cells

“…Figure 1 d shows the external quantum effi ciency (EQE) curves of the three devices made from CF only, CF-1% DIO, and CF-3% DCB Tremendous progress has been made in the fi eld of organic photovoltaic cells (OPVs) in the past few years, with the highest reported power conversion effi ciencies (PCEs) reaching over 10%. [1][2][3] These achievements have been realized through chemical structure modifi cation on donors and acceptors, [4][5][6] improvement in active-layer processing methods, [7][8][9][10] interfacial morphology control, [11][12][13] and device structure engineering.…”

Donor Materials for Organic Solar Cell (OSC)

“…Recently, researchers started to use fluoro substituted benzothiadiazole (F-BT) for the OPV polymer synthesis [31][32][33][34][35][36][37][38][39][40][41][42]. The use of F-BT instead of BT as the acceptor unit for polymer synthesis can make polymers with planar polymer chain conformation and low energy levels.…”