B ← N Coordination Enables Efficient p-Doping in a Pyrazine-Based Polymer Donor Toward Enhanced Photovoltaic Performance

Herein, we reveal a p-doping method in an organic semiconductor through the intermolecular B <- N coordination to realize improvement of hole mobilities and the corresponding photovoltaic performance enhancement. For this purpose, we first design and synthesize a pyrazine-based polymer containing N atoms in the backbone, namely, poly[4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl) benzo [1,2-b:4,5-b'] dithiophene-co-3-dodecylthiophene-co-pyrazine] (PBP-Cl). Then, we realize the p-doping to PBP-Cl readily using a boron-Lewis acid dopant (tris(pentafluorophenyl)borane, BCF), which can form the intermolecular B <- N coordination and enhance the carrier mobilities by a factor of ca. 2.0-fold. The B <- N coordination-induced p-doping effect was further applied in PBP-Cl/Y6-based organic solar cells (OSCs) and realized an impressive device performance enhancement from 13.70 to 15.17%. This work proves an innovative and effective path toward high-performance OSCs using boron-Lewis acids to dope the nitrogen-based active layers via B <- N coordination.

Automated summary

In this study, p-doping of an organic semiconductor was achieved through intermolecular B <- N coordination, leading to improved carrier mobilities and photovoltaic performance. The use of a boron-Lewis acid dopant in a nitrogen-based polymer resulted in a significant enhancement of device performance in organic solar cells.