Phenoxy-(Chloro)_n-Boron Subnaphthalocyanines: Alloyed Mixture, Electron-Accepting Functionality, and Enhanced Solubility for Bulk Heterojunction Organic Photovoltaics

Abstract

The first set of phenoxy BsubNc compounds, PhO-Cl n BsubNc and F 5 -Cl n BsubNc, was synthesized through an axial displacement reaction of Cl-Cl n BsubNc with phenol and pentafluorophenol (respectively). Like their precursor, the products were found to be an alloyed mixture of phenoxylated Cl n 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 n BsubNc. Although the phenoxylation of Cl-Cl n 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 ( V OC ) was observed, ultimately exceeding 1.0 V when phenoxylated Cl n 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 n BsubNcs, when paired with poly-3-hexylthiophene, also showed high V 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 n 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 n BsubNcs into BHJ OPVs.

Boron Subphthalocyanines and Silicon Phthalocyanines for Use as Active Materials in Organic Photovoltaics

“…When α‐6T was paired with the differently synthesized Cl‐Cl n BsubNcs (Figure ), it was discovered that higher degree of chlorination resulted in more efficient devices with PCE's ranging between 2.44 % and 4.32 % . Phenoxy‐BsubNc compounds (PhO‐Cl n BsubNc and F 5 ‐Cl n BsubNc, Figure b)) were synthesized in a subsequent study and also incorporated as electron acceptors in OPVs . A V OC exceeding 1.0 V was achieved in PHJ devices, but with less than half of the PCEs achieved for the commercial Cl‐Cl n BsubNc.…”

Outdoor Stability of Chloro–(Chloro)n–Boron Subnaphthalocyanine and Chloro–Boron Subphthalocyanine as Electron Acceptors in Bilayer and Trilayer Organic Photovoltaics

“…The use of a planar heterojunction (PHJ) architecture limits the influence of morphology on device performance, making PHJ OPVs an ideal architecture to test material stability. Two similar classes of materials have been demonstrated to perform exceptionally well as electron-accepting fullerene replacements in laboratory-scale, planar heterojunction (PHJ) OPVs: boron subnaphthalocyanines (BsubNcs) and boron subphthalocyanines (BsubPcs). − BsubNcs and BsubPcs have many synthetic handles for tuning performance, and synthetic procedures for achieving many different derivatives have already been demonstrated. ,,− We recently determined that BsubNcs actually consist of an alloyed mixture of chlorinated species (Cl n BsubNc), a mixture that benefits their OPV performance . We also previously conducted small-scale outdoor tests on some BsubPc derivatives, determining that phenoxy and phenyl substituents in the axial position of a BsubPc significantly harm their outdoor stability relative to the prototypical Cl–BsubPc. , Cnops et al demonstrated a record power conversion efficiency of 8.4% for a PHJ OPV can be achieved by combining chloro–Cl n BsubNc (Cl–Cl n BsubNc) and chloro–BsubPc (Cl–BsubPc) with sexithiophene (α-6T) .…”

Exploring the Effects of Bay Position Chlorination on the Emissive Properties of Chloro-(Chloro)n-Boron Subnaphthalocyanines for Light Emission.

“…Boron subnaphthalocyanines (BsubNcs, Figure 1) are a subgroup of the phthalocyanine macrocyclic family, which have attracted interest as functional organic semiconductors [1][2][3][4] and sensor materials [5] because of their synthetic tunability [6][7][8][9] and high thermal, chemical and photo-stability. [10][11][12] Structurally BsubNcs, and their counterparts boron subphthalocyanine (BsubPc), [13] differ from conventional metal-and metalloid-phthalocyanines (MPcs) [14] because of their molecular non-planar conformation and reduced trimeric ligand structure.…”

“…[4] It has also been shown that mixed alloyed composition remains constant on further chemical derivatization of Cl-ClnBsubNc and enables their integration into bulk-heterojunction OPVs. [9] In contrast with the developments in OPVs, far fewer reports exist on the applications of BsubPcs showing a mixture of host (Alq3) and guest emission, with a peak EQE 0.41% . [34] Given the potential of Cl-ClnBsubNc as light emitting materials, we wish to understand the influence on the degree of bay-position chlorination on their luminescence properties.…”