Phenoxy-(Chloro)_<i>n</i>-Boron Subnaphthalocyanines: Alloyed Mixture, Electron-Accepting Functionality, and Enhanced Solubility for Bulk Heterojunction Organic Photovoltaics

The first set of phenoxy BsubNc compounds, PhO-Cl_<i>n</i>BsubNc and F₅-Cl_<i>n</i>BsubNc, was synthesized through an axial displacement reaction of Cl-Cl_<i>n</i>BsubNc with phenol and pentafluorophenol (respectively). Like their precursor, the products were found to be an alloyed mixture of phenoxylated Cl_<i>n</i>BsubNcs with random positioning in the solid state yet consistent frequency of bay position chlorination. The average bay position chlorine occupancy was determined to be 0.99 through single crystal diffraction of PhO-Cl_<i>n</i>BsubNc. Although the phenoxylation of Cl-Cl_<i>n</i>BsubNc did not influence the chromophore photophysical properties, the electrochemical behavior was found to be more stable. Phenoxylation yielded differences in organic photovoltaic (OPV) device metrics. Specifically, a significant increase in open circuit voltage (<i>V</i>_OC) was observed, ultimately exceeding 1.0 V when phenoxylated Cl_<i>n</i>BsubNcs were paired with alpha-sexithiophene (α-6T) in planar heterojunction OPVs. Phenoxylation enabled the first example of BsubNcs incorporated into polymer-based bulk heterojunction (BHJ) OPVs through enhanced solubility. Phenoxylated Cl_<i>n</i>BsubNcs, when paired with poly-3-hexylthiophene, also showed high <i>V</i>_OC in BHJ OPVs with broad spectral absorption up to 760 nm. In the BHJ case, simple phenoxy was shown to be a better axial substituent compared to pentafluorophenoxy. This study represents the first example of using Cl_<i>n</i>BsubNcs with nonchlorine axial substituents in OPVs and demonstrates that phenoxylation has a significant impact on device metrics while enhancing solubility to enable incorporation of Cl_<i>n</i>BsubNcs into BHJ OPVs