Medium-Bandgap Conjugated Polymers Containing Fused Dithienobenzochalcogenadiazoles: Chalcogen Atom Effects on Organic Photovoltaics

Abstract

We designed, synthesized, and characterized a series of three medium-bandgap conjugated polymers (PBDT­fDTBO, PBDT­fDTBT, and PBDT­fDTBS) consisting of fused dithienobenzo­chalcogenadiazole (fDTBX)-based weak electron-deficient and planar building blocks, which possess bandgaps of ∼2.01 eV. The fDTBX-based medium-bandgap polymers exhibit deep-lying HOMO levels (∼5.51 eV), which is beneficial for use in multijunction polymer solar cell applications. The resulting polymers with chalcogen atomic substitutions revealed that the difference in the electron negativity and atomic size of heavy atoms highly affects an intrinsic property, morphological feature, and photovoltaic property in polymer solar cells. The polymer solar cells based on sulfur-substituted medium-bandgap polymer showed power conversion efficiencies above 6% when blended with [6,6]-phenyl-C71-butyric acid methyl ester in a typical bulk-heterojunction single cell. These results suggest that the fDTBX-based medium-bandgap polymer is a promising alternative material for P3HT in tandem polymer solar cells for achieving high efficiency.

18% Efficiency organic solar cells

“…1a) [30]. In continuing our effort, here we report a more efficient copolymer donor D18 by using a fused-ring acceptor unit, dithieno[3 0 ,2 0 :3,4;2 00 ,3 00 :5,6]benzo[1,2-c][1,2,5]thiadiazole (DTBT) [40]. Compared with DTTP, DTBT has a larger molecular plane and gifts D18 a higher hole mobility.…”

Medium‐Bandgap Conjugated Polymer Donors for Organic Photovoltaics

“…Taking advantage of solar energy is one of the effective methods to save energy. As a clean‐energy technology, organic photovoltaics (OPVs) have attracted considerable attention for their advantages of light‐weight, low cost, solution processability, and applications for large area devices . In the past decades, tremendous efforts has been devoted to the innovation of OPVs.…”

A High‐Performance Non‐Fullerene Acceptor Compatible with Polymers with Different Bandgaps for Efficient Organic Solar Cells

“…To realize a highly efficient OSC, a wide light harvesting range, an appropriate energy level alignment between donor and acceptor, and an near‐ideal active layer morphology are essentially needed . To this end, a variety of polymers with different bandgaps ( E g s), e.g., the wide‐bandgap (WBG: E g > 1.8 eV), the medium‐bandgap (MBG: 1.6 < E g < 1.8 eV), and the low‐bandgap (LBG: Eg < 1.6 eV) polymers, were developed to pair with the dominant fullerene acceptors ([6,6]‐phenyl‐C61/C71‐butyric acid methyl ester: PC 61 BM/PC 71 BM) in the past decades. In such systems, PC 61 BM/PC 71 BM acting as a universal electron acceptor show good compatibility with a number of different bandgap polymers, and achieved over 10% power conversion efficiencies (PCEs) in combination with polymers such as PBT1‐EH ( E g = 1.84 eV), PffBT4T‐C 9 C 13 ( E g = 1.65 eV), and PTB7‐Th ( E g = 1.58 eV) .…”