N → B Ladder Polymers Prepared by Postfunctionalization: Tuning of Electron Affinity and Evaluation as Acceptors in All-Polymer Solar Cells

Abstract

A poly(biphenylene−pyrazinylene) (PPz, E g opt = 3.10 eV) and a head-to-tail regioregular polypyridine (rr-P4Py, E g opt = 3.25 eV) equipped with 1-alkenyl side chains have been prepared and postfunctionalized by hydroboration with different hydroboranes (9H-BBN, (C 6 F 5) 2 B-H (BPF-H), Cl 2 B-H) to give the corresponding ladder polymers featuring intramolecular coordinative N → B bonds. Characterization of the optical and electrochemical properties of the postfunctionalized polymers shows that the borylation strongly increases their electron affinity and lowers the optical gaps. Electron affinities between −3.75 eV (PPzBBN, E g opt = 2.16 eV) and −4.35 eV (PPzBPF, E g opt = 2.07 eV) can be reached for hydroborated PPz, while rr-P4Py-derivatives reach LUMO levels of −3.45 eV (P4PyBBN, E g opt = 2.88 eV), −3.85 eV (P4PyBPF, E g opt = 2.95 eV), and −4.15 eV (P4PyBCl 2 , E g opt = 2.95 eV). The potential of this class of compounds as electron acceptors is demonstrated by the investigation of the semiconducting properties of PPzBBN and PPzBPF, which showed ambipolar charge transport with hole and electron mobilities in order of 2 × 10 −5 cm 2 V −1 s −1. The polymers were tested as acceptors in all-polymer solar cells, which yielded functioning devices, with open-circuit voltages that directly reflect the electron affinity of the employed acceptor.

Conformation Control of Conjugated Polymers

“…Soona fterward, the Pammer group reported a stable, fully locked conjugated polymer (11), synthesized via the same strategy in 2019( Scheme4b). [35] To avoid potential steric congestion of side chains,6 -(1-alkenyl)-side-chains in precursor PPy 10 was placed in the 4-position rather than the previous2 -position. Thus, after hydroboration, N!Bc oordinative bonds would be placed alternately on both sides of the chain backbone.…”

N–B ← N Bridged Bithiophene: A Building Block with Reduced Band Gap to Design n-Type Conjugated Polymers

“…All-PSCs use blends of polymeric donors and polymeric acceptors as the photoactive layer. Compared with solar cells based on organic small molecules or inorganic semiconductors, all-PSCs have great advantages in terms of solution processing, low cost, flexibility. ,,, The bottleneck of all-PSCs development is the lack of polymeric electron acceptors. BN-X1 and BN-X2 exhibit low-lying LUMO and HOMO energy levels and broad absorption spectra, indicating that they are suitable for application as electron acceptors in all-PSCs.…”

“…Organoboron chemistry provides new tools to design π-conjugated molecules and polymers. − Jäkle’s, Chujo’s, Pammer’s, Huang’s groups, and our group have made great progress on organoboron A-type building blocks for conjugated polymers. The resulting polymers have been successfully used in OLEDs, OFETs, and OSCs. − ,− Herein, we report a new A-type building block for conjugated polymers, namely, N–B←N bridged bithiophene (BNTzT). Its chemical structure is shown in Scheme .…”

Trendbericht: Makromolekulare Chemie

“…Sie kommen als Akzeptormaterialien in organischen Solarzellen infrage. 30) In den letzten Jahren wurden selbstheilende Polymere etwa für Beschichtungen diskutiert, aber auch als Hochleistungsmaterialien.…”