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Sequence‐defined synthetic oligomers and polymers provide unprecedented opportunities for polymer chemists to finely control properties such as chain folding, self‐assembly, and optoelectronic performance of materials. However, absolute control over both chain‐length and monomer sequence has been a long‐standing "grand challenge" for decades. Herein, we report a novel strategy to synthesize monodisperse sequence‐defined conjugated oligomers in a homogeneous manner by temperature cycling, thereby achieving single‐monomer precision in conjugated polyheterocycles. A series of sequence‐defined oligomers with up to twelve repeating units, four different monomers, and various sequences were successfully synthesized. Monomer sequence was also proved to affect optical properties. We believe this strategy not only exhibits general applicability to the synthesis of group 16 conjugated oligomers and polymers, but also has far‐reaching potential for other polymer systems. [ABSTRACT FROM AUTHOR]

We report 4,4-difluoro-4 H-cyclopenta[2,1-b:3,4-b′]dithiophene (fCDT) as a new electron-rich unit to design polymer electron acceptors. Owing to the fluoro substitutes, fCDT unit exhibits downshifted LUMO energy level, diminished steric hindrance effect and strong intermolecular interaction. The resulting polymer electron acceptor exhibits low-lying LUMO energy level and high electron mobility, as well as good all-polymer solar cell device performance. [ABSTRACT FROM AUTHOR]

We demonstrate that polymer electron acceptors with excellent all-polymer solar-cell (all-PSC) device performance can be developed from polymer electron donors by using B←N units. By alleviating the steric hindrance effect of the bulky pendant moieties on the conjugated polymers that contain B←N units, the π-π stacking distance of polymer backbones is decreased and the electron mobility is consequently enhanced by nearly two orders of magnitude. As a result, the power conversion efficiency of all-PSCs with the polymer acting as the electron acceptor is greatly improved from 0.12 % to 5.04 %. This PCE value is comparable to that of the best all-PSCs with state-of-the-art polymer acceptors. [ABSTRACT FROM AUTHOR]

Indoor photovoltaics (IPVs) are receiving great attention because they can power the wireless microelectronic devices needed for Internet of Things (IoTs) applications. Many polymer acceptors have been designed and synthesized for solar cell applications. In this manuscript, we study the application of three polymer acceptors in all-polymer indoor photovoltaic devices. The polymer acceptors containing boron-nitrogen coordination bond (B←N) have medium bandgap of 1.8–1.9 eV and proper the lowest unoccupied molecular orbital energy level (E LUMO) and the highest occupied molecular orbital energy level (E HOMO) alignment and consequently are very suitable for IPV application. Under fluorescent lamp illumination at the brightness of 2000 lux, the devices based on the polymer acceptors containing B←N unit show the open-circuit voltage of 1.08 V and a power conversion efficiency (PCE) of 23.2%. This performance is much higher than that of other imide-based polymer acceptors with small bandgap and wide absorption spectrum. The polymer acceptors containing B←N unit, which have medium bandgap of 1.8–1.9 eV and exhibit absorption spectra mainly in the visible region, are suitable for all-polymer indoor photovoltaic application. [Display omitted] • The polymer acceptors for efficient indoor photovoltaic should have medium bandgap. • The polymer acceptors containing B←N unit are suitable for indoor photovoltaic. • Suppressing trap-assisted recombination is significant to indoor photovoltaic. [ABSTRACT FROM AUTHOR]