BN Embedded Polycyclic π-Conjugated Systems: Synthesis, Optoelectronic Properties, and Photovoltaic Applications

Abstract

In the periodic table of elements, boron (B, atomic number, 5) and nitrogen (N, atomic number, 7) are neighboring to the carbon (C, atomic number, 6). Thus, the total electronic number of two carbons (12) is equal to the electronic sum of one boron (5) and one nitrogen (7). Accordingly, replacing two carbons with one boron and one nitrogen in a π-conjugated structure gives an isoelectronic system, i.e., the BN perturbed π-conjugated system, comparing to their all-carbon analogs. The BN embedded π-conjugated systems have unique properties, e.g., optical absorption, emission, energy levels, bandgaps, and packing order in contrast to their all-carbon analogs and have been intensively studied in terms of novel synthesis, photophysical characterizations, and electronic applications in recent years. In this review, we try to summarize the synthesis methods, optoelectronic properties, and progress in organic photovoltaic (OPV) applications of the representative BN embedded polycyclic π-conjugated systems. Firstly, the narrative will be commenced with a general introduction to the BN units, i.e., B←N coordination bond, B-N covalent bond, and N-B←N group. Then, the representative synthesis strategies toward π-conjugated systems containing B←N coordination bond, B-N covalent bond, and N-B←N group will be summarized. Afterwards, the frontier orbital energy levels, optical absorption, packing order in solid state, charge transportation ability, and photovoltaic performances of typical BN embedded π-conjugated systems will be discussed. Finally, a prospect will be proposed on the OPV materials of BN doped π-conjugated systems, especially their potential applications to the small molecules organic solar cells.

Unpredicted Concentration-Dependent Sensory Properties of Pyrene-Containing NBN-Doped Polycyclic Aromatic Hydrocarbons

“…[ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. However, these outstanding BN- and BNB-doped π-systems suffer from synthesis methods involving rigorous reaction conditions (e.g., air and/or moisture free), multiple steps and unsatisfied total yield [ 33 , 34 , 35 , 36 , 37 , 38 ].…”

B←N Coordination: From Chemistry to Organic Photovoltaic Materials

“…Fusing the B←N bonds symmetrically into the conjugated systems through electrophilic borylation creates B←N‐bridged units with ladder‐type and coplanar backbones. Several synthetic methodologies have been developed for electrophilic borylation, [ 71–76 ] which tends to occur on aromatic cycles, hydroxyl, or amine groups, producing C–B←N, O–B←N, or N–B←N‐bridged units, respectively ( Figure ). The substituents (X) on the B centers can be halos, Ph, Mes, or C 6 F 5 .…”

Going beyond the borders: pyrrolo[3,2-b]pyrroles with deep red emission

“…compounds in which two adjacent carbons in a π-conjugated core have been replaced by one boron and one N/O atom. 23–28 Of particular importance are π-conjugated systems containing a B–N covalent bond, B←N coordination bond 29 and N–B←N motif, as evidenced by growing number of reports dealing with BN-embedded heteroacenes 29–32 and BODIPY analogues, 33–37 mostly due to their excellent performance in OLEDs 38 a and OPVs. 38 b , c They were also computed to possess inverted singlet-triplet gap.…”