Solar Energy Materials Research Articles

(Invited) Optical Properties and Active Plasmon Excitations in 2D Materials

The control and tuning of the optical properties of materials and the localization of electromagnetic energy are long standing quests for scientists. Not only it allows to design new classes of adaptive devices such as smart windows but also to perform surface enhanced vibrational spectroscopies such a SERS.For metallic nanostructured systems, the optical properties are directly related to collective electronic excitation (plasmons) and they depend mainly on the composition, shape and size of the system. Doped semiconductors such as Indium Tin Oxide have been also shown to display active plasmon, i.e., optical excitations that can be easily controlled by an external stimulus, e.g. a static electric potential [1].In 2D materials, an electrostatic doping is common due to the low density of state at the Fermi energy. Moreover, anisotropy plays a very specific role [2] and surface plasmon became 1D plasmon. In this presentation, based on numerical simulations, we analyze the plasmon excitation associated to edge of 2D materials or to metallic mirror twin boundaries in Transition Metal Dichalcogenide [3]. Doped graphene [4] nanodots or shape engineering in wrinkled structures will also be discussed.[1] A. Maho et al. Solar Energy Materials and Solar Cells 200 (2019) 110014[2] B. Majerus et al. Phys. Rev. B 98 (2018) 125419[3] A. A. Koos et al. J. Phys. Chem 123 (2019) 24855[4] F. Joucken et al. Phys. Rev. Mat. 3 (2019) 110301

(Invited) Luminescence of Rare Earth Doped Si Based Nanofilms for LED and Photovoltaic Applications

Rare earth (RE) doped silicon host matrices have been largely investigated to produce their luminescence's at different wavelengths for many applications such as Light Emitting Diode (LED) or frequency conversion layer to improve Solar Cells (SCs) efficiency. To achieve such a goal, RE ions-doped silicon oxynitride-based (SiOxNy) films have been deposited by reactive magnetron co-sputtering. A oxynitride host matrix allows a high RE ions incorporation while avoiding the clustering effect observed in silicon oxide host matrix.In a first step, two different RE, Tb3+ and Ce3+, have been investigated. The Tb3+ ions present intra 4f transitions, whereas the Ce3+ ions have 4f-5d transitions. [1] These two different electronic configurations are investigated by means of luminescence spectroscopy. Indeed, the first step of this work is motivated by achieving an intense emission of Tb3+ and Ce3+ ions by optimizing the deposition parameters. The SiOxNy: RE layers were deposited on silicon substrates by using RF magnetron sputtering technique under N2 reactive flow, with a typical thickness of 20-50 nm. A deep investigation is performed to obtain an intense Ce3+ photoluminescence signal according to the Ce and N concentrations. Up to 6 at. % of Ce3+, no saturation of the PL intensity has been observed, demonstrating the absence of Ce clusters and/or silicate phase formation thanks to the nitrogen content. The influence of the nitrogen on current injection will be presented and the electroluminescence (EL) properties (I-V characteristic, EL spectra) will be analyzed.[2] In a second step, down-converter (DC) layers compatible with the silicon industry which absorb UV photons and convert them into IR ones at an energy just above the Si band gap, were developed, taking account these two donors Tb3+ and Ce3+ and as acceptor the Yb3+ ion. Two different co-doping have been chosen i.e. Tb3+-Yb3+ and Ce3+-Yb3+ with the aim at obtaining an intense emission of the Yb3+ at 980 nm (1.265 eV). Furthermore the excitation mechanisms of acceptor ions Yb3+ will be discussed in both cases. [3, 4] At last, efficiency measurements with our DC layers on homemade and industrial Si-SCs have been carried out.[5] [1] C. Labbé, Y.T. An, G. Zatryb, X. Portier, A. Podhorodecki, P. Marie, C. Frilay, J. Cardin, F. Gourbilleau, Structural and emission properties of Tb3+-doped nitrogen-rich silicon oxynitride films, Nanotechnology, 28 (2017) 115710-115714. [2] F. Ehre, C. Labbé, C. Dufour, W. Jadwisienczak, J. Weimmerskirch-Aubatin, X. Portier, J.-L. Doualan, J. Cardin, A. Richard, D.C. Ingram, C. Labrugère, F. Gourbilleau, Nitrogen concentration effect on Ce doped SiOxNy emission: towards optimized Ce3+ for DEL application Nanoscale, 20 (2018) 4818-4830. [3] Y.-T. An, C. Labbé, M. Morales, F. Gourbilleau, Highly efficient infrared quantum cutting in Tb3+-Yb3+ codoped silicon oxynitride for solar cell applications, Advanced Optical Materials, 1 (2013) 855-862. [4] L. Dumont, P. Benzo, J. Cardin, I.S. Yu, C. Labbé, P. Marie, C. Dufour, G. Zatryb, A. Podhorodecki, F. Gourbilleau, Down-shifting Si-based layer for Si solar applications, Solar Energy Materials and Solar Cells, 169 (2017) 132-144. [5] L. Dumont, J. Cardin, C. Labbé, C. Frilay, P.-M. Anglade, I.S. Yu, M. Vallet, P. Benzo, M. Carrada, D. Stiévenard, H. Mérabet, F. Gourbilleau, First Down Converter multilayers integration in an industrial Si solar cell process, Progress in Photovoltaics: Research and Applications, 27 (2018) 152-162.

METHOD FOR MANUFACTURING THIN FILMS OF CUBI2O4 FOR PHOTOELECTROCHEMICAL APPLICATIONS

A method has been developed for producing thin semiconductor films of a complex copper-bismuth system (CuBi2O4) with reduced roughness and increased photoactivity. The application process is carried out under standard laboratory conditions from aqueous solutions of salts, takes advantage of centrifugation to evenly distribute the coating over the surface, is characterized by low material consumption, and allows the thin nanocrystalline layers formation with a given thickness. Polyethylene glycol (PEG) is used to improve the spraying of solution droplets over the entire surface of the CuBi2O4 film, which allows the dense uniform films deposition. Scanning electron and atomic force microscopy data demonstrate the ordering of the growth of CuBi2O4 particles (size ≈200 nm) and a 1.5-fold decrease in the roughness of the relief when polyethylene glycol is added to the solution. Micrographs show the growth of uniformly sized rounded crystallites. In a comparative analysis of the XRD diagram of the samples, an increase in the number and intensity of peaks corresponding to the crystalline phase of Kusachiite (CuBi2O4) with the introduction of PEG into the initial solution is observed. Based on the photoelectrochemical measurements results, it was found that the addition of polyethylene glycol to the electrolyte helps to increase the photoactivity of the samples by 2 times. The obtained thin polycrystalline CuBi2O4 films are promising for use in photoelectrochemical converters. Keywords: Solar energy material, spin coating, CuBi2O4, polyethylene glycol.

Nitride-Based Interfacial Layers for Monolithic Tandem Integration of New Solar Energy Materials on Si: The Case of CZTS

The monolithic tandem integration of third-generation solar energy materials on silicon holds great promise for photoelectrochemistry and photovoltaics. However, this can be challenging when it involves high-temperature reactive processes, which would risk damaging the Si bottom cell. One such case is the high-temperature sulfurization/selenization in thin film chalcogenide solar cells, of which the kesterite Cu2ZnSnS4 (CZTS) is an example. Here, by using very thin (<10 nm) TiN-based diffusion barriers at the interface, with different composition and properties, we demonstrate on a device level that the protection of the Si bottom cell is largely dependent on the barrier layer engineering. Several monolithic CZTS/Si tandem solar cells with open-circuit voltages (Voc) up to 1.06 V and efficiencies up to 3.9% are achieved, indicating a performance comparable to conventional interfacial layers based on transparent conductive oxides, and pointing to a promising alternative design in solar energy conversion devices.

In-situ/operando soft x-ray spectroscopy characterization of energy and catalytic materials

The capabilities of soft x-ray absorption (XAS), soft x-ray emission spectroscopy (XES), resonant inelastic soft x-ray scattering (RIXS), and their application to characterization of solar energy materials are presented. We have discussed some recent developments of in-situ soft x-ray spectroscopy cells, which enable the investigation of critical solid/liquid or solid/gas interfaces in chemical and electrochemical processes under real-world practical conditions. In particular, in-situ soft x-ray spectroscopies can be utilized to probe the formation of intermediate species, charge separation upon illumination of sunlight and electron transfer to the interfacial reactions. A number of examples using soft x-ray spectroscopies to study these solar energy and catalytic materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the energy conversion and energy storage systems.

Sol-gel solution-processed Cu2SrSnS4 thin films for solar energy harvesting

According to theory calculation, the Cu2SrSnS4 (CSTS) become a candidate material for harvesting solar energy via either photovoltaic (PV) or photoelectrochemical (PEC) paths due to its efficient light-absorbing capability (high absorption coefficients above 104 cm−1), earth-abundant, nontoxic constituents, and suitable defect properties. As a new material, there is a long way to accomplish the application of CSTS. Film preparation of CSTS are very critical. In this work, CSTS thin films were synthesized by a sol-gel based solution process. The obtained CSTS films showed trigonal structure with band gap of 1.93 eV and p-type conductivity. By comparing the CSTS thin films synthesized with different annealed temperature and Sr/Sn atomic ratios, we confirmed that sulfurization annealing at 600 °C and Sr/Sn atomic ratios of 1.15 yields relatively high quality CSTS films. A PEC cell using the CSTS thin film as working electrode were established and a saturated photocurrent of ∼0.5 mA/cm2 had been achieved. It has also been applied to a PV device, demonstrating open-circuit voltage of 296 mV and power conversion efficiency of 0.164%. Pinholes in the films and reef-like grains at the surface of CSTS films were likely to limit the devices performance. The feasibility of solar energy harvesting of CSTS material was demonstrated.

Strain-induced band modulation and excellent stability, transport and optical properties of penta-MP2 (M = Ni, Pd, and Pt) monolayers.

First principle calculations utilizing density functional theory were carried out to investigate the electronic, transport and optical properties of penta-MP2 (M = Ni, Pd and Pt) monolayer compounds under applied uniaxial and biaxial tensile strains. With an optimum magnitude of applied strain, we found band gap transitions in penta-MP2 monolayers from zero/narrow to the semiconductor regime, wherein band gaps were noticed to be firmly dependent on the applied uniaxial and biaxial tensile strains. In this study, the PBE approach was used primarily to evaluate electronic properties, from where the identified architectures of penta-MP2 with maximum obtained bandgaps under respective optimum strains were assessed through the HSE06 method of calculation for better estimation of band gaps and optical properties. Prior to HSE calculations, we affirmed our assessment for the stability and reliability of the compounds under uniaxial and biaxial strains of up to 15% through phonon spectrum and elastic calculations. A distinct transition was also noted from semiconductor to metal for all compounds after the applied optimum uniaxial and biaxial strains. The optical absorption spectra in all the stretched penta-MP2 compounds reached the order of 106 cm−1, with significant peaks belonging to the IR and visible regions; this indicates promising applications of these materials in high-performance solar energy and good hot mirror materials. The enhanced I–V responses under uniaxial and biaxial tensile strains using the non-equilibrium Green's function (NEGF) approach confirm the usefulness of the strained state of the considered penta-MP2 monolayers. The results show that tuning electronic properties, I–V characteristics and optical properties of stretched penta-MP2 compounds under tensile strain merits significant future applications in optoelectronic devices and as good hot mirror materials.

Crystallization of Ge in ion-irradiated amorphous-Ge/Au thin films

Herein, the structural, optical, and electrical properties of Au-induced crystallization in amorphous germanium (a-Ge) thin films are presented for future solar energy material applications.

An assessment on crystallization phenomena of Si in Al/a-Si thin films via thermal annealing and ion irradiation.

In the present study, crystallization of amorphous-Si (a-Si) in Al/a-Si bilayer thin films under thermal annealing and ion irradiation has been investigated for future solar energy materials applications. In particular, the effect of thickness ratio (e.g. in Al : a-Si, the ratio of the Al and a-Si layer thickness) and temperature during irradiation on crystallization of the Si films has been explored for the first time. Two sets of samples with thickness ratio 1 : 1 (set-A: 50 nm Al/50 nm a-Si) and thickness ratio 1 : 3 (set-B: 50 nm Al/150 nm a-Si) have been prepared on thermally oxidized Si-substrates. In one experiment, thermal annealing of the as-prepared sample (of both the sets) has been done at different temperatures of 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. Significant crystallization was found to initiate at 200 °C with the help of thermal annealing, which increased further by increasing the temperature. In another experiment, ion irradiation on both sets of samples has been carried out at 100 °C and 200 °C using 100 MeV Ni7+ ions with fluences of 1 × 1012 ions per cm2, 5 × 1012 ions per cm2, 1 × 1013 ions per cm2, and 5 × 1013 ions per cm2. Significant crystallization of Si was observed at a remarkably low temperature of 100 °C under ion irradiation. The samples irradiated at 100 °C show better crystallization than the samples irradiated at 200 °C. The maximum crystallization of a-Si has been observed at a fluence of 1 × 1012 ions per cm2, which was found to decrease with increasing ion fluence at both temperatures (i.e. 100 °C & 200 °C). The crystallization of a-Si is found to be better for set-B samples as compared to set-A samples at all the fluences and irradiation temperatures. The present work is aimed at developing the understanding of the crystallization process, which may have significant advantages for designing crystalline layers at lower temperature using appropriate masks for irradiation at the desired location. The detailed mechanisms behind all the above observations are discussed in this paper.

Double perovskite Cs4CuSb2Cl12 microcrystalline device for cost effective photodetector applications

Recently reported double perovskites (DPs), Cs4CuSb2Cl12 has led to the development of a new lead free perovskite. It is 1 eV band gap material. The perovskite microcrystals were synthesized via liquid phase method. This was investigated as active solar energy materials for visible-light photodetector. The microcrystalline device was made in a single-step printable Cs4CuSb2Cl12/carbon materials composite paste. 10 wt% active material composite was found to be the best candidate for the highest responsivity, 10-3 A/W and detectivity, 108 J. One-step printing of the composite paste can be used for cost effective photodetector applications.

Exploring interface confined water flow and evaporation enables solar-thermal-electro integration towards clean water and electricity harvest via asymmetric functionalization strategy

Water evaporation is a ubiquitous phenomenon in nature. To fully explore the solar-enabled water evaporation can effectively alleviate the growing concern of shortage of water and also energy source. Although significant advances have been achieved for alternative combination of multifunctional applications to explore the unexploited or wasted thermal/solar energy. However, it remains a great challenge for an effective integration of desired functions into one photo-thermal material for extensive harvesting solar energy. Herein, interfacial confined water flow and evaporation are rationally explored to realize an efficient combination of solar-heating enhanced water-flow-induced power generation and interfacial water evaporation. The effective solar-thermal-electro integration is enabled by one multifunctional Janus material via an asymmetric functionalization strategy. As a proof-of-concept, a bilayer carbon nanotubes (CNTs) film/cellulose paper is employed to function as an efficient solar-driven evaporator. Moreover, the as-prepared CNTs-based paper can be further asymmetrically decorated with hydrophobic polydimethylsiloxane (PDMS) and utilized to collect electricity from the directional water flow under dark and light condition. The monolithic design concept is expected to effectively utilize the water evaporation process for integrated electricity and clean water generation.

PHOTOVOLTAICS LITERATURE SURVEY (No. 154)

In order to help readers stay up‐to‐date in the field, each issue of Progress in Photovoltaics will contain a list of recently published journal articles that are most relevant to its aims and scope. This list is drawn from an extremely wide range of journals, including IEEE Journal of Photovoltaics, Solar Energy Materials and Solar Cells, Renewable Energy, Renewable and Sustainable Energy Reviews, Journal of Applied Physics, and Applied Physics Letters. To assist readers, the list is separated into broad categories, but please note that these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions please email Ziv Hameiri at ziv.hameiri@unsw.edu.au.

Comments on the paper: “Thermoelectric properties and thermal stress simulation of pressureless sintered SiC/AlN ceramic composites at high temperatures” published by Dina H.A. Besisa in Solar Energy Materials & Solar Cells 182 (2018) 302–313

We find it necessary to contribute by the addendum to a serious and objective scientific discussion on the relationship between Seebeck coefficient and electrical resistivity with the change of doping amount. In the comment, we argue that Seebeck coefficient and electrical resistivity of the solid materials must theoretically vary simultaneously with the changing doping amount as this phenomenon has been observed in previous publications [1–4]. However, in the recent report (Solar Energy Materials & Solar Cells, 2018, 182, 302–313),αand ρ show a negative correlation with changing doping amount, which is invalid conclusion because it is based on a mistake. Apart from the wrong correlation, we also contend that the formula used to calculate the ZT was wrongly stated (from line 3 to line 9 on page 304)[5], which introduces doubts about their results. The figure of merit of thermoelectric material is given by ZT=α2σκT, where α is the Seebeck coefficient; σ is the electrical conductivity; κ is the thermal conductivity; T is the absolute temperature. We equally observe a considerable discrepancy between descriptions and experimental results as demonstrated from line 1 to line 7 on page 307, which disagrees with Figs. 6 and 7 in Ref. 5.

Exciton Dissociation and Suppressed Charge Recombination at 2D Perovskite Edges: Key Roles of Unsaturated Halide Bonds and Thermal Disorder.

Two-dimensional (2D) Ruddlesden-Popper perovskites form a new class of solar energy materials with high performance, low cost and good stability. Nonradiative electron-hole recombination is the main source of charge and energy losses, limiting material efficiency. Experiments show that edge states in 2D halide perovskites accelerate exciton dissociation into long-lived charge carriers, improving performance. Using a combination of nonadiabatic molecular dynamics and time-domain density functional theory, we demonstrate that unsaturated chemical bonds of iodine atoms at perovskite edges is the main driving force for hole localization. Chemically unsaturated Pb atoms confine electrons to a much lesser extent, because they more easily support different oxidation states and heal chemical defects. This difference between defects associated with metals and nonmetals is general to many nanoscale systems. Thermal atomic fluctuations play important roles in charge localization, even in the bulk region of 2D perovskite films, a phenomenon that is different from polaron formation. Charge localization at edges is robust to thermal excitation at ambient conditions. The separated charges live a long time, because the nonadiabatic coupling between the excited and ground states is small, under 1 meV, and quantum coherence is short, less than 10 fs. The calculations agree very well with the time-resolved optical measurements on both luminescence lifetime and line width. The detailed understanding of the excited state dynamics in the 2D halide perovskites generated by the simulations highlights the unique chemical properties of these materials, and provides guidelines for design of efficient and inexpensive solar energy materials.

Study of photovoltaic solar materials development trend by deductive logic method using big data

In recent years, the development of solar materials in the field of science and technology has experienced many major breakthroughs. This study collects relevant data to evaluate the development of solar energy technology based on deductive reasoning approach in the popular types, and then utilize big data to investigate the trend of smart materials development in solar energy research. This study aims to understand the impact of materials science on the development of photovoltaic solar energy and understand the trends in the research field from the number of published journals in past years.The period of study in this paper is from 1970 to 2018. The research scope is limited to an analysis of solar journals from Web of Science®, which indicates that various solar materials have very obvious difference in growth trends.From 1970 to 2010, although the United States was the country with the largest number of published solar journals, the percentage gradually decreased. Then from 2011 to 2018, China became the first among the top countries in solar energy materials publications.Among them, the field of “Dye-sensitized solar” grew the most, the highest research publications in the field of solar energy research is “Materials science”.

An excellent heterojunction nanocomposite solar-energy material for photocatalytic transformation of hydrogen sulfide pollutant to hydrogen fuel and elemental sulfur: A mechanistic insight

Hydrogen sulfide (H2S) is a noxious gas for living organisms and devastating/corrosive agent for metallic structures, which is generated in large scale through natural [geothermal/bacterial] activities or industrial processes, particularly by petroleum and gas industries. Photocatalytic elimination of this plentiful-perilous pollutant and its transformation into hydrogen green fuel and elemental sulfur is a novel/sustainable strategy, which is intriguing from energy and environmental science as well as technological viewpoints. To this end, the design and synthesis of low-price, environmentally friendly, effective photocatalyst/solar-energy materials are highly in demand. Herein, through a facile hydrothermal route, a set of new pn junction xBi2S3·yMnS nanocomposite photocatalysts were synthesized and employed in an alkaline H2S medium (pH = 11) to generate hydrogen fuel and elemental sulfur under atmospheric pressure at room temperature conditions. The maximum conversion yield was attained at the molar ratio xy=2, where the photocatalyst exhibited the lowest charge recombination, strong photon absorption, and the greatest surface area among the synthesized nanocomposite materials. Furthermore, it was witnessed that disulfide (S22-) was the only oxidation product in the reaction medium, which could be effortlessly precipitated as elemental sulfur by acidification of the medium and lowering the pH to about 5.

Carbon Assisted Methylammonium Lead Iodide Microcrystalline Device for an Inexpensive Self-Powered Photodetector

Organometallic halide perovskite as Methyl Ammonium Lead iodide (MAPbI3) is the basis of current focus of solar energy materials research. Here we report acetophenone assisted pure phase MAPbI3 powder crystals synthesis for fabrication of inexpensive self-powered photodetector. The as fabricated photodetector ascertain, response time of 200 ms with detectivity ∼8.2 × 1011 jones at zero bias voltage and the SNR ∼4 × 103 under white light illumination intensity (19 mW/cm2). Wt% variation of MAPbI3 reveals that 20 wt% of the perovskite crystals in carbon matrix is better candidate for a compatible photodetector.

Photocatalytic Conversion of CO2 into Oxygenate Fuels/Chemicals Using Efficient, Eco-Friendly, Titania/Hematite-Based Nanostructured Solar-Energy Materials

Photocatalytic hydrogenation of carbon dioxide (CO₂), using water feedstock (H source), sunlight and appropriate semiconducting low-cost/eco-friendly/solar-energy materials, is a promising route for sequestration of this greenhouse gas and its conversion into value-added oxygenate fuels (compounds). Herein, by employing three hematite-based nanostructured photocatalyst/solar-energy materials, the CO₂ photoreduction (hydrogenation) process was carried out inside a water photosplitting reactor, and various oxygenate (C/H/O) products [including ethanol, methanol and formaldehyde as well as oxalic, acetic and formic acids] were synthesized in the reaction medium. Concerning the complexity of system and the diversity of products-being photocatalytically synthesized during the photoconversion process, two straightforward problem-solving strategies were proposed [one, focusing on a single/particular product and pursuing its quantity (concentration) at different illumination periods, and the other, simultaneous investigation of various products being produced at a fixed reaction period, in the aqueous or gas-phase medium]. Finally, the matter of CO₂ photoconversion into oxygenate fuels/chemicals was explained in detail from photoelectrochemical [semiconductor band structure and redox potential] as well as mechanistic perspectives.

Strategies of Anode Materials Design towards Improved Photoelectrochemical Water Splitting Efficiency

This review presents the latest processes for designing anode materials to improve the efficiency of water photolysis. Based on different contributions towards the solar-to-hydrogen efficiency, we mainly review the strategies to enhance the light absorption, facilitate the charge separation, and enhance the surface charge injection. Although great achievements have been obtained, the challenges faced in the development of anode materials for solar energy to make water splitting remain significant. In this review, the major challenges to improve the conversion efficiency of photoelectrochemical water splitting reactions are presented. We hope that this review helps researchers in or coming to the field to better appreciate the state-of-the-art, and to make a better choice when they embark on new research in photocatalytic water splitting.

Electrochemical Advances in Boron Subnaphthalocyanines (BsubNcs) for Organic Photovoltaic Applications: The Ambient Stability of Bsubnc Mixed Alloys; Their Separation and Electrochemical Properties; And Chemical Progresses Towards Pure Bsubncs to Yield Their Individual Electrochemical Evaluation

For some time, our group has been focused on the design, synthesis and application of derivatives of boron subphthalocyanines (BsubPcs). Our focal point has been and continues to be equally between the basic chemistry of BsubPcs and their application in organic electronic devices with a focus on two specific device applications, organic photovoltaics (OPVs)/solar cells[1,2] and organic light emitting diodes (OLEDs). More recently, we have taken an equal approach to derivatives similar to BsubPcs, boron subnaphthalocyanines (BsubNcs); BsubNcs being unique and beneficial materials for OPV application.[3] We have recently shown that BsubNcs actually become randomly chlorinated during their synthetic preparation and actually then form a mixed alloy composition of chlorinated materials, which we have designated as Cl-ClnBsubNcs.[4] The mixed alloy composition is unique, and has been determined to be a mixture of 24 (more or less) chlorinated BsubNcs that despite being a mixture form single crystals. The formation of single crystals is enabled by the chlorine atoms occupying vacancies within the solid state structure, the vacancies being the so-called “bay position” of the BsubNcs structure. After establishing the correlation of electrochemical characteristics and OPV performance for Cl-ClnBsubNcs, we have recently shown that phenoxylated versions of ClnBsubNc are also a mixed alloy and applicable in BHJ OPVs also as electron accepting materials.[5] We have also shown that Cl-ClnBsubNcs when applied as electron donating materials in OPVs have the same performance correlations to the amount of chlorination present.[6] We have also shown that BsubNcs are equally stable within an OPV in the ambient environment compared with BsubPcs.[7] This accumulation of properties led us to consider how to separate the alloyed mixtures and how to prepare pure BsubNcs. During this presentation I will describe a chemical pathway to enable the separation of the mixed alloys of BsubNcs. We found that not all 24 (more or less) isomers can be separated, yet this process has enabled a more detailed electrochemical characterization and correlation to amount of halogenation. I will also describe a chemical pathway to pure BsubNcs, avoiding halogenation/chlorination in the bay position. This pathway enables a detailed characterization of a pure BsubNc including its electrochemical properties. Finally, if completed by the presentation time, I will also describe a chemical pathway to enable complete halogenation of the bay-position of a BsubNc. This pathway then enabled the characterization and therefore the impact on the electrochemical and other physical properties of complete bay-position halogenation. Co-authors/investigators will be identified during this presentation. References. [1] “Outdoor Performance and Stability of Boron Subphthalocyanines Applied as Electron Acceptors in Fullerene-Free Organic Photovoltaics.” Josey, D.; et al, ACS Energy Lett., 2017, 2 (3), 726–732. DOI: 10.1021/acsenergylett.6b00716. [2] “Boron Subphthalocyanines as Electron Donors in Outdoor Lifetime Monitored Organic Photovoltaic Cells.” Garner, R.K.; et al, Solar Energy Materials and Solar Cells, 2018 176, 331-335. DOI: 10.1016/j.solmat.2017.10.018 [3] “8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer” Cnops, K.; et al., Nature Comm., 5, Article number: 3406, DOI:10.1038/ncomms4406. [4] “The mixed and alloyed chemical composition of chloro-(chloro)n-boron subnaphthalocyanines dictates their physical properties and performance in organic photovoltaics.” Dang, J.D.; et al, J. Mat. Chem. A., 2016, 4, 9566-9577. [5] “Phenoxy-(chloro)n-boron subnaphthalocyanines; alloyed mixture, electron-accepting functionality, enhanced solubility for bulk heterojunction organic photovoltaics” Dang, J.D.; et al, ACS Omega, 2018, 3(2), 2093–2103. DOI: 10.1021/acsomega.7b01892. [6] “The Mixed Alloyed Chemical Composition of Chloro-(chloro)n-Boron Subnaphthalocyanines Dictates Their Performance as Electron-Donating and Hole-Transporting Materials in Organic Photovoltaics” Garner, R.K.; et al, ACS Appl. Energy Materials, 2017, 1(3), 1029-1036. DOI: 10.1021/acsaem.7b00180. [7] "Outdoor Stability of Chloro-(Chloro)n-Boron Subnaphthalocyanine and Chloro-Boron Subphthalocyanine as Electron Acceptors in Bilayer and Trilayer Organic Photovoltaics" Josey, D.; et al, ACS Applied Energy Materials, 2018, submitted. Figure 1