earned a B.S. degree in chemistry from the University of Dayton in 2001 and as an undergraduate worked on conductive polymer syntheses at the Air Force Research Laboratory at Wright Patterson Air Force Base. He completed an M.S. degree in 2004 and Ph.D. degree in 2008 at Portland State University and joined the Lewis group at Caltech in 2008. He is currently an NSF-ACCF postdoctoral fellow (2009) and has been studying the electrical characteristics of inorganic semiconductors in contact with conductive polymers. His research interests include molecular semiconductors for solar energy conversion, porphyrin macrocycles for optoelectronic applications, and catalyst materials for photoelectrolysis. Emily L. Warren received a B.S. in chemical engineering at Cornell University in 2005. She received an M.Phil in Engineering for Sustainable Development from Cambridge University in 2006. She is currently a graduate student in Chemical Engineering at the California Institute of Technology. Her research interests include semiconductor photoelectrochemistry, solar energy conversion, and semiconductor nanowires. She is currently a graduate student in Chemical Engineering at the California Institute of Technology, working under Nathan S. Lewis. James R. McKone is in his third year of graduate studies in the Division of Chemistry and Chemical Engineering at the California Institute of Technology, working under Nathan S. Lewis and Harry B. Gray. In 2008 he graduated from Saint Olaf College with a Bachelor of Arts degree, double-majoring in music and chemistry. His current research focuses on semiconductor-coupled heterogeneous catalysis of the hydrogen evolution reaction using mixtures of earth-abundant transition metals. Shannon W. Boettcher earned his B.A. degree in chemistry from the University of Oregon, Eugene (2003), and, working with Galen Stucky, his Ph.D. in Inorganic Chemistry from the University of California, Santa Barbara (2008). Following postdoctoral work with Nate Lewis and Harry Atwater at the California Institute of Technology (2008-2010), he returned to the University of Oregon to join the faculty as an Assistant Professor. His research interests span synthesis and physical measurement with the goal of designing and understanding solid-state inorganic material architectures for use in solar-energy conversion and storage.

Figure S1. Panel (a) shows the J-E data collected for the electrode fabricated with 'enhanced' absorption due to light-trapping elements, in 0.5 M aq. H 2 SO 4 under ELH-type W-halogen solar simulation. Panel (b) shows a cross-sectional SEM image of the same sample. Panel (c) compares the spectral response collected for the sample with light-trapping elements ('enhanced') versus the spectral response for the normal sample. The red response in the 'enhanced' cell is significantly improved. Panel (d) shows the increased J sc with reduced angle dependence, for the enhanced sample compared to the normal sample. Panel (e) shows a digital photograph of a normal Pt/n + p-Si wire-array electrode evolving hydrogen under ~ 1 sun illumination. Small bubbles can be seen nucleating on the wire-array surface. The larger bubbles are stuck on the epoxy, and are the result of the coalescence of many small bubbles. S1

This review summarizes recent advances in the use of porphyrins, phthalocyanines, and related compounds as components of solar cells, including organic molecular solar cells, polymer cells, anddye-sensitized solar cells. The recent report of a porphyrin dye that achieves 11% power conversion efficiency in a dye-sensitized solar cell indicates that these classes of compounds can be as efficient as the more commonly used ruthenium bipyridyl derivatives.

The synthesis, electrochemical, and photophysical characterization of N,N'-dialkylated and N,N'-dibenzylated dipyridinium thiazolo[5,4-d]thiazole derivatives are reported. The thiazolothiazole viologens exhibit strong blue fluorescence with high quantum yields between 0.8-0.96. The dioctyl, dimethyl, and dibenzyl derivatives also show distinctive and reversible yellow to dark blue electrochromism at low reduction potentials. The fused bicyclic thiazolo[5,4-d]thiazole heterocycle allows the alkylated pyridinium groups to remain planar, strongly affecting their electrochemical properties. The singlet quantum yield is greatly enhanced with quaternarization of the peripheral 4-pyridyl groups (Φ increases from 0.22 to 0.96) while long-lived fluorescence lifetimes were observed between 1.8-2.4 ns. The thiazolothiazole viologens have been characterized using cyclic voltammetry, UV-visible absorbance and fluorescence spectroscopy, spectroelectrochemistry, and time-resolved photoluminescence. The electrochromic properties observed in solution, in addition to their strong fluorescent emission properties, which can be suppressed upon 2 e reduction, make these materials attractive for multifunctional optoelectronic, electron transfer sensing, and other photochemical applications.

The optical absorption, ionic conductivity, electronic conductivity, and gas separation properties have been evaluated for flexible composite films of ionically conductive polymers that contain partially embedded arrays of ordered, crystalline, p-type Si microwires. The cation exchange ionomer Nafion, and a recently developed anion exchange ionomer, poly(arylene ether sulfone) that contains quaternary ammonium groups (QAPSF), produced composite microwire array/ionomer membrane films that were suitable for operation in acidic or alkaline media, respectively. The ionic conductivity of the Si wire array/ Nafion composite films in 2.0 M H 2 SO 4 (aq) was 71 mS cm À1, and the conductivity of the Si wire array/ QAPSF composite films in 2.0 M KOH(aq) was 6.4 mS cm À1. Both values were comparable to the conductivities observed for films of these ionomers that did not contain embedded Si wire arrays. Two Si wire array/Nafion membranes were electrically connected in series, using a conducting polymer, to produce a trilayer, multifunctional membrane that exhibited an ionic conductivity in 2.0 M H 2 SO 4 (aq) of 57 mS cm À1 and an ohmic electrical contact, with an areal resistance of $0.30 U cm 2 , between the two physically separate embedded Si wire arrays. All of the wire array/ionomer composite membranes showed low rates of hydrogen crossover. Optical measurements indicated very low absorption (<3%) in the ionexchange polymers but high light absorption (up to 80%) by the wire arrays even at normal incidence, attesting to the suitability of such multifunctional membranes for application in solar fuels production.

Porphyrins substituted at meso positions with aminophenyl groups undergo oxidative electropolymerization in a process analogous to the formation of polyaniline. Porphyrins that successfully generate polymer films on the electrode include those tetrasubstituted with four p-aminophenyl groups, trisubstituted, or transdisubstituted, but not cis-disubstituted or monosubstituted. The polymerization process is monitored independently by cyclic voltammetry, absorption spectroscopy, and an electrochemical quartz crystal microbalance. The mechanism is considered analogous to aniline polymerization, except that attack of electrophilic nitrogens must occur at ortho positions of another aminophenyl group. Reflectance FT-IR and resonance Raman spectroscopy detect the presence of diphenylamine, dihydrophenazine, and phenazine linkages in the porphyrin polymer film from tetra(4-aminophenyl)porphyrin (TAPP). TAPP polymerized in dichloromethane (DCM) with added pyridine gradually passivates; i.e., electronic conductivity diminishes and polymer growth levels off (the films are light yellow). Without added pyridine, electronic conductivity is sustained and film growth continues to a thick black film. Diphenylamine and dihydrophenazine linkages were common in films whose electroactivity remained constant throughout the film growth process while phenazine linkages were prevalent in films where passivation and loss of electrochemical activity had occurred. It is proposed that overoxidation to the phenazine structures leads to loss of electronic conductivity, analogous to formation of pernigraniline in polyaniline. The morphology of poly-TAPP is a highly interconnected nanofibrous network, with fiber diameters in the range 40-100 nm, with somewhat different structures depending on polymerization conditions.

111)-oriented p + Si wafers with a resistivity of ρ<0.003 Ω-cm, were coated with 300 nm of thermal oxide (Silicon Quest International). The samples were then patterned with square arrays of 3 µm circular holes, with a hole-to-hole pitch of 7 µm, using a positive photoresist layer (Microchem S1813). The exposed SiO 2 was etched

The versatility of porphyrins as optoelectronic or catalytic units makes them attractive elements for inclusion in functional materials. Polymers that include porphyrins have been created with a wide variety of structures and used in a wide range of applications. This review covers recent developments in the synthesis, characterization and applications of polymeric materials in which porphyrins are key components of the repeat units, including the rapidly growing area of metal-organic frameworks and related covalent organic frameworks. © 2015 Society of Chemical Industry Keywords: review; porphyrin; metal-organic framework; covalent organic framework PORPHYRINS AS FUNCTIONAL BUILDING BLOCKSThe porphyrin ring and its many structural relatives are common functional units in both natural and synthetic systems (Fig. 1). Porphyrins have a variety of properties that allow them to be useful in applications, especially their broad-ranging optoelectronic and catalytic capabilities. Furthermore, these properties are readily modulated by incorporation of various metals inside the ring or by substituent effects at various locations around the ring. In many cases, nature provides guidance for specific structure-function correlations and applications -the so-called biomimetic approaches. In nature, porphyrin (heme) units are typically embedded in a biological matrix that controls the environment of and access to the porphyrin. In synthetic systems, porphyrins in polymeric matrices have been developed in similar fashion to help control the specific application.In this review, we briefly cite previous reviews and summarize recent results regarding the synthesis, structure, properties and applications of polymeric porphyrins. We only include polymers that contain multiple porphyrin units as an integral part of the polymer, as opposed to polymeric matrices that are simply used to encapsulate individual porphyrin units. We also cover the rapidly growing field of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), where they specifically include porphyrins as a key component of the framework. Structures related to porphyrins (phthalocyanines, corroles, chlorins, etc.) and porphyrin dimers are not covered, but some porphyrin oligomers are discussed; reviews on many of these are available in the comprehensive series Handbook of Porphyrin Science.