Regioregular Narrow‐Bandgap n‐Type Polymers with High Electron Mobility Enabling Highly Efficient All‐Polymer Solar Cells

Abstract

Narrow‐bandgap n‐type polymers with high electron mobility are urgently demanded for the development of all‐polymer solar cells (all‐PSCs). Here, two regioregular narrow‐bandgap polymer acceptors, L15 and MBTI, with two electron‐deficient segments are synthesized by copolymerizing two dibrominated fused‐ring electron acceptors (FREA) with distannylated aromatic imide, respectively. Taking full advantage of the FREA and the imide, both polymer acceptors show narrow bandgap and high electron mobility. Benefiting from the more extended absorption, better backbone ordering, and higher electron mobility than those of its regiorandom analog, the L15‐based all‐PSC yields a high power conversion efficiency (PCE) of 15.2% when blended with the polymer donor PM6. More importantly, MBTI incorporating a benzothiophene‐core FREA segment shows relatively higher frontier molecular orbital levels than L15, forming a cascade‐like energy level alignment with L15 and PM6. Based on this, ternary all‐PSCs are designed where MBTI is introduced as a guest into the PM6:L15 host system. Thanks to further optimal blend morphology and more balanced charge transport, the PCE is improved up to 16.2%, which is among the highest values for all‐PSCs. The results demonstrate that combining an FREA and an aromatic imide to construct regioregular narrow‐bandgap polymer acceptors provides an effective approach to fabricate highly efficient all‐PSCs.

n-Type Organic and Polymeric Semiconductors Based on Bithiophene Imide Derivatives

“…To our delight, all polymers exhibited better device stability than PBTI attributed to their greatly suppressed LUMOs (−3.63 to −4.11 eV) versus that (−3.48 eV) of PBTI. 43 PCNDTI with the deepest LUMO (−4.11 eV) showed the highest OTFT stability, retaining 60% of its initial mobility after 360 h of storage under ambient conditions, which is superior to that of most n-type polymers in the literature, 44 demonstrating the power of cyano functionalization for lowering FMOs. The deep-lying LUMOs of these polymers should be advantageous for n-doping.…”

“…It should be pointed out that these polymers suffer from limited absorption at long wavelengths, which severely restrains J sc in all-PSCs. Inspired by the great success of the polymerization strategy of fused-ring electron acceptors (FREAs) and the synthesis of BTI-Tin, we developed A–A copolymer L15 (Figure ), , which can synergistically combine the excellent light absorption of FREAs and the advantages of BTI to enable a polymer acceptor with broad absorption, good solubility, and a promising electron-transport property. When mingled with PM6, L15-based all-PSCs delivered a high PCE of 15.2% with a remarkable J sc of 22.2 mA cm –2 , which is among the highest values for all-PSCs.…”

Polymerizing small molecular acceptors for efficient all‐polymer solar cells

“…(c) Linkage unit modulation . As reported, introducing an acceptor moiety as a linkage unit to form A‐A‐type PSMAs provides the additional electron channels for securing high electron mobility 20,29 . This design strategy offers new opportunities to deeply investigate the effect of suitable linkage units (D/A) on charge dynamics.…”

“…As reported, introducing an acceptor moiety as a linkage unit to form A-A-type PSMAs provides the additional electron channels for securing high electron mobility. 20,29 This design strategy offers new opportunities to deeply investigate the effect of suitable linkage units (D/A) on charge dynamics. In addition, our recent works also provide the valuable information on how halogenation of the linkage unit in PSMAs could effectively regulate the solid-state crystallinity and blend morphology, thus improving electron mobility and performance.…”

Exploring Inorganic Hole Collection Materials from Mixed‐Metal Dawson‐Type Polyoxometalates for Efficient Organic Photovoltaic Devices

“…Organic solar cells (OSCs) have been considered as emerging technologies for the next generation of photovoltaic devices with the advantages of low‐cost manufacturing on lightweight flexible substrates by solution fabrication methods. [ 1–5 ] Benefitting from the great progress in organic photoactive layer materials, the power conversion efficiency (PCE) has exceeded 15%, indicating a bright future for the practical applications of OSCs. [ 6–10 ] In OSCs, the electrode interlayer between the photoactive layer and electrode plays a crucial role in enhancing the PCEs by facilitating charge collection.…”