Evaluating thiophene electron-donor layers for the rapid assessment of boron subphthalocyanines as electron acceptors in organic photovoltaics: solution or vacuum deposition?

In this study, we consider the choice of a standard electron-donating material to be paired with boron subphthalocyanines (BsubPcs) to rapidly assess the viability of new BsubPc derivatives as electron-accepting materials within organic photovoltaic devices (OPVs). Specifically, we evaluate the effectiveness of solution-cast poly(3-hexylthiophene-2,5-diyl) (P3HT) as an electron donor paired with BsubPc derivatives relative to vacuum-deposited sexithiophene (α-6T). By using fullerene (C60 ), boron subphthalocyanine chloride (Cl-BsubPc), and hexachloro boron subphthalocyanine chloride (Cl-Cl6 BsubPc) as electron acceptors, we find that devices made with α-6T outperform those with P3HT. However, the two thiophene-based materials show the same performance trends. Given the preservation of these trends, we can recommend either option for assessing the potential of new BsubPc derivatives; P3HT as a solution-cast electron-donor layer or α-6T as a vacuum-deposited alternative.

Characterization of µ-oxo-(BsubPc)2 in Multiple Organic Photovoltaic Device Architectures: Comparing against and Combining with Cl-BsubPc.

We demonstrate the first application of a unique boron subphthalocyanine (BsubPc) derivative, the oxygen bridged dimer µ-oxo-(BsubPc)2, as a multifunctional material within planar heterojunction organic photovoltaic (OPV) devices. We first explored the pairing of µ-oxo-(BsubPc)2 with well-known electron accepting and electron donating materials to explore its basic functionality. These preliminary device structures and metrics indicated that µ-oxo-(BsubPc)2 is best applied as an electron donating material when used in simple bilayer structures, as it yielded comparable OPV device efficiencies to that of the more well-established and highly optimized chloro-boron subphthalocyanine (Cl-BsubPc) OPV device structures. Thereafter we established that the HOMO/LUMO energy levels of µ-oxo-(BsubPc)2 are well-placed to apply it as a bifunctional donor/acceptor interlayer material in both energy and charge cascade OPV device architectures. Within this context, we found that µ-oxo-(BsubPc)2 was particularly effective in a charge cascade device as an interlayer between Cl-BsubPc and C70. We finally found evidence of an alloying-like effect for devices with mixed electron donor layers of (Cl-BsubPc) and µ-oxo-(BsubPc)2, achieved through co-deposition. The overarching conclusion is therefore that µ-oxo-(BsubPc)2 has the ability to improve the performance of Cl-BsubPc OPV devices and is a multifunctional material worthy of further study.

Boron Subphthalocyanines as Triplet Harvesting Materials within Organic Photovoltaics.

Singlet fission, the generation of two excited triplet states from a single absorbed photon, is currently an area of significant interest to photovoltaic researchers. In this Letter, we outline how a polychlorinated boron subphthalocyanine, previously hypothesized to be an effective harvester of singlet fission derived triplets from pentacene, is relatively efficient at facilitating the process. As expected, we found a major increase in photocurrent generation at the expense of device voltage. For a direct point of comparison, we also have paired the same polychlorinated boron subphthalocyanine with α-sexithiophene to probe the alternative technique of complementary absorption engineering. The sum of these efforts have let us present new guidelines for the molecular design of boron subphthalocyanine for organic photovoltaic applications.

Assessing the potential roles of silicon and germanium phthalocyanines in planar heterojunction organic photovoltaic devices and how pentafluoro phenoxylation can enhance π-π interactions and device performance.

In this study, we have assessed the potential application of dichloro silicon phthalocyanine (Cl2-SiPc) and dichloro germanium phthalocyanine (Cl2-GePc) in modern planar heterojunction organic photovoltaic (PHJ OPV) devices. We have determined that Cl2-SiPc can act as an electron donating material when paired with C60 and that Cl2-SiPc or Cl2-GePc can also act as an electron acceptor material when paired with pentacene. These two materials enabled the harvesting of triplet energy resulting from the singlet fission process in pentacene. However, contributions to the generation of photocurrent were observed for Cl2-SiPc with no evidence of photocurrent contribution from Cl2-GePc. The result of our initial assessment established the potential for the application of SiPc and GePc in PHJ OPV devices. Thereafter, bis(pentafluoro phenoxy) silicon phthalocyanine (F10-SiPc) and bis(pentafluoro phenoxy) germanium phthalocyanine (F10-GePc) were synthesized and characterized. During thermal processing, it was discovered that F10-SiPc and F10-GePc underwent a reaction forming small amounts of difluoro SiPc (F2-SiPc) and difluoro GePc (F2-GePc). This undesirable reaction could be circumvented for F10-SiPc but not for F10-GePc. Using single crystal X-ray diffraction, it was determined that F10-SiPc has significantly enhanced π-π interactions compared with that of Cl2-SiPc, which had little to none. Unoptimized PHJ OPV devices based on F10-SiPc were fabricated and directly compared to those constructed from Cl2-SiPc, and in all cases, PHJ OPV devices based on F10-SiPc had significantly improved device characteristics compared to Cl2-SiPc.

Green-sensitive organic photodetectors with high sensitivity and spectral selectivity using subphthalocyanine derivatives.

Green-sensitive organic photodetectors (OPDs) with high sensitivity and spectral selectivity using boron subphthalocyanine chloride (SubPc) derivatives are reported. The OPDs composed of SubPc and dicyanovinyl terthiophene derivative (DCV3T) demonstrated the highest green-sensitivity with maximum external quantum efficiency (EQE) of 62.6 % at an applied voltage of -5 V, but wide full-width-at-half-maximum (FWHM) of 211 nm. The optimized performance considering spectral selectivity was achieved from the composition of N,N-dimethyl quinacridone (DMQA) and SubPc showing the high specific detectivity (D*) of 2.34 × 10(12) cm Hz(1/2)/W, the EQE value of 60.1% at -5 V, and narrow FWHM of 131 nm. In spite of the sharp absorption property of SubPc with the maximum wavelength (λmax) at 586 nm, the EQE spectrum showed favorable green-sensitivity characterized by smooth waveform with λmax at 560 nm, which is induced from the high reflectance of SubPc centered at 605 nm. The photoresponsivity of the OPD devices was found to be consistent with their absorptance. Optimized DMQA/SubPc device showed the lowest value of blue crosstalk (0.42) and moderate red crosstalk (0.37), suggesting its promising application as a green-sensitive OPD.

Pentafluorophenoxy boron subphthalocyanine as a fluorescent dopant emitter in organic light emitting diodes.

A fluorinated phenoxy boron subphthalocyanine (BsubPc) is shown to function as a fluorescent dopant emitter in small molecule organic light emitting diodes (OLEDs). Narrow electroluminescence (EL) emission with a full width at half-maximum of ∼30 nm was observed regardless of the host used, indicating that this narrow EL is intrinsic to the BsubPc molecule. A bathochromic shift and the growth of a new EL peak at higher wavelengths with increasing doping concentration were found to be a result of molecular aggregation. Excitation of BsubPc by direct charge trapping as well as Förster resonant energy transfer were shown using different host molecules. A maximum efficiency of 1.5 cd/A was achieved for a 4,4'-N,N'-dicarbazole-biphenyl (CBP) host.