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Coordination of growth and division in eukaryotic cells is essential for populations of proliferating cells to maintain size homeostasis, but the underlying mechanisms that govern cell size have only been investigated in a few taxa. The green algaChlamydomonas reinhardtii(Chlamydomonas) proliferates using a multiple fission cell cycle that involves a long G1 phase followed by a rapid series of successive S and M phases (S/M) that produces 2ndaughter cells. Two control points show cell-size dependence: Commitment in mid-G1 phase requires attainment of a minimum size to enable at least one mitotic division during S/M, and the S/M control point where mother cell size governs cell division number (n), ensuring that daughter distributions are uniform.tny1mutants pass Commitment at a smaller size than wild type and undergo extra divisions during S/M phase to produce small daughters, indicating that TNY1 functions to inhibit size-dependent cell cycle progression.TNY1encodes a cytosolic hnRNP A- related RNA binding protein and is produced once per cell cycle during S/M phase where it is apportioned to daughter cells, and then remains at constant absolute abundance as cells grow, a property known as subscaling (1). Altering the dosage ofTNY1in heterozygous diploids or through overexpression increased Commitment cell size and daughter cell size, indicating that TNY1 is a limiting factor for both size control checkpoints. Epistasis placedTNY1function upstream of the retinoblastoma tumor suppressor complex (RBC) and one of its regulators, Cyclin-Dependent Kinase G1 (CDKG1) (2). Moreover, CDKG1 protein and mRNA were found to over-accumulate intny1cells suggesting that CDKG1 may be a direct target of repression by TNY1. Our data expand the potential roles of subscaling proteins outside the nucleus and imply a control mechanism that ties TNY1 accumulation to pre-division mother cell size.Author SummarySize control is a fundamental property of cells which requires balancing cell growth with cell division, but the mechanisms used by cells to achieve this balance are only partly understood. The best-characterized mechanisms for size control to date involve fixed amounts of nuclear- DNA-bound inhibitory factors which repress cell division until cells grow past a minimum size threshold to overcome the inhibition. The unicellular green alga Chlamydomonas and many other algae and protists use a non-canonical cell cycle where cells can grow by many-fold in size before dividing, and then undergo multiple fission which involves successive rapid divisions to produce a uniform-sized population of daughters. In Chlamydomonas an unknown size homeostasis mechanism couples mother cell size to division number such that larger mother cells divide more times than smaller mother cells. Here, we identified and characterized a key factor governing size control in Chlamydomonas, a cytoplasmic RNA-binding protein and division inhibitor, TNY1, that is produced in a fixed amount in daughter cells and does not increase with cell growth, a property called sub-scaling. We found that TNY1 represses production of a cell cycle activator, CDKG1, during multiple fission to control daughter cell size. TNY1 is the first example of a cytosolic cell cycle inhibitor that does not depend on nuclear DNA binding to govern sub-scaling.

Fair and meaningful device per- formance comparison among luminescent solar concentrator- photovoltaic (LSC-PV) reports cannot be realized without a gen- eral consensus on reporting stan- dards in LSC-PV research. There- fore, it is imperative to adopt standardized characterization protocols for these emerging types of PV devices that are consistent with other PV devices. This commentary highlights several common limitations in LSC literature and summarizes the best practices moving for- ward to harmonize with standard PV reporting, considering the greater nuances present with LSC-PV. Based on these prac- tices, a checklist of actionable items is provided to help stan- dardize the characterization/re- porting protocols and offer a set of baseline expectations for au- thors, reviewers, and editors. The general consensus combined with the checklist will ultimately guide LSC-PV research towards reliable and meaningful ad- vances.

Chenchen Yang joined the materials science program at Michigan State University in 2015 to work under Prof. Lunt in the Molecular and Organic Excitonics Lab. He earned his B.E. from the University of Electronic Science and Technology of China in 2012. Then he obtained his M.S. from the University of Florida in 2015. His current research focuses on transparent solar cell synthesis, fabrication, and characterization. Dianyi Liu obtained his Ph.D. in inorganic chemistry from Lanzhou University in 2009. He then worked as a postdoc at Peking University, the University of Saskatchewan, and Michigan State University. He began as an assistant professor at Westlake University in January 2019. His research interests include flexible electronics, optoelectronic materials, and devices. Richard R. Lunt is the Johansen Crosby Endowed Professor at Michigan State University in the Departments of Chemical Engineering & Materials Science and Physics. He earned his B.S. from the University of Delaware and his Ph.D. from Princeton University. He then worked as a post-doctoralresearcher at MIT. His group focuses on understanding and exploiting excitonic photophysics and molecular crystal growth to develop unique thin-film optoelectronic devices. He is known for his pioneering work on transparent solar cells and concentrators.

Chenchen Yang joined the materials science program at Michigan State University in 2015 to work under Prof. Lunt in the Molecular and Organic Excitonics Lab. He earned his B.E. from the University of Electronic Science and Engineering of China in 2012. Then, he obtained his M.S. from University of Florida in 2015. His current research focuses on transparent solar cell synthesis, fabrication, and characterization. Dianyi Liu obtained his PhD in inorganic chemistry from Lanzhou University in 2009. He then worked as a postdoc at Peking University, the University of Saskatchewan, and Michigan State University. He began as an assistant professor at Westlake University in January 2019. His research interests include flexible electronics, optoelectronic materials, and devices. Matthew Bates is a graduate student in chemical engineering at Michigan State University working in the Molecular and Organic Excitonic Lab led by Prof. Lunt. He received his B.S. in chemical engineering from Oregon State University in 2016. He is focused on developing transparent photovoltaics. Miles Barr is co-founder and Chief Technology Officer at Ubiquitous Energy in Redwood City, CA. He earned his bachelor’s degree from Vanderbilt University and his Ph.D. from the Massachusetts Institute of Technology, both in chemical engineering. He then co-founded Ubiquitous Energy and has grown the company through pilot manufacturing, serving as both CEO and CTO. His team is currently working to develop, scale up, and commercialize transparent solar technology for a variety of end applications. Richard R. Lunt is the Johansen Crosby Endowed Professor at Michigan State University in the Departments of Chemical Engineering & Materials Science and Physics. He earned his B.S. from the University of Delaware and his PhD from Princeton University. He then worked as a post-doctoral researcher at MIT. His group focuses on understanding and exploiting excitonic photophysics and molecular crystal growth to develop unique thin-film optoelectronic devices. He is known for his pioneering work on transparent solar cells.

Visibly transparent luminescent solar concentrators (TLSCs) can convert existing window glazing systems and non-window surfaces into solar energy harvesting resources, dramatically improving energy utilization efficiency. While there has been a significant interest in improving the power conversion efficiency, little attention has been focused on the challenges of integrating luminescent solar concentrators (LSCs) onto non-window surfaces or windows with significant infrared absorption coefficients. In these situations, the total internal reflection (TIR) can be effectively disabled when LSCs are directly and seamlessly integrated onto surfaces that are highly absorptive or scattering to infrared light. To overcome this challenge, we utilize a low refractive index adhesive film with high transparency between the TLSC waveguide and the back surface, to maintain both the device functionality and aesthetic quality of the surface underneath. Photovoltaic measurements were conducted to show that the TIR is re-enabled with the presence of such a structure. Thus, this method can effectively improve LSC performance and scalability, and allows TLSCs to be integrated onto arbitrary surfaces such as automobiles, billboards, and buildings.

Transparent photovoltaic (TPV) devices have a number of unique advantages compared with opaque photovoltaic devices. However, balancing efficiency and transparency has been difficult. To date, few ...

With growing populations and pressing environmental problems, future economies will be increasingly plant-based. Now is the time to reimagine plant science as a critical component of fundamental science, agriculture, environmental stewardship, energy, technology and healthcare. This effort requires a conceptual and technological framework to identify and map all cell types, and to comprehensively annotate the localization and organization of molecules at cellular and tissue levels. This framework, called the Plant Cell Atlas (PCA), will be critical for understanding and engineering plant development, physiology and environmental responses. A workshop was convened to discuss the purpose and utility of such an initiative, resulting in a roadmap that acknowledges the current knowledge gaps and technical challenges, and underscores how the PCA initiative can help to overcome them., National Science Foundation 1916797 David W Ehrhardt, Kenneth D Birnbaum, Seung Yon Rhee; National Science Foundation 2052590 Seung Yon Rhee

Journal of the American Chemical Society 142(41), 17681 - 17692 (2020). doi:10.1021/jacs.0c08352, Conjugated polymers are regarded as promising candidates for dopant-free hole-transport materials (HTMs) in efficient and stable perovskite solar cells (PSCs). Thus far, the vast majority of polymeric HTMs feature structurally complicated benzo[1,2-b:4,5-b’]dithiophene (BDT) analogs and electron-withdrawing heterocycles, forming a strong donor–acceptor (D–A) structure. Herein, a new class of phenanthrocarbazole (PC)-based polymeric HTMs (PC1, PC2, and PC3) has been synthesized by inserting a PC unit into a polymeric thiophene or selenophene chain with the aim of enhancing the $π–π$ stacking of adjacent polymer chains and also to efficiently interact with the perovskite surface through the broad and planar conjugated backbone of the PC. Suitable energy levels, excellent thermostability, and humidity resistivity together with remarkable photoelectric properties are obtained via meticulously tuning the conformation and elemental composition of the polymers. As a result, PSCs containing PC3 as dopant-free HTM show a stabilized power conversion efficiency (PCE) of 20.8% and significantly enhanced longevity, rendering one of the best types of PSCs based on dopant-free HTMs. Subsequent experimental and theoretical studies reveal that the planar conformation of the polymers contributes to an ordered and face-on stacking of the polymer chains. Furthermore, introduction of the “Lewis soft” selenium atom can passivate surface trap sites of perovskite films by Pb–Se interaction and facilitate the interfacial charge separation significantly. This work reveals the guiding principles for rational design of dopant-free polymeric HTMs and also inspires rational exploration of small molecular HTMs., Published by American Chemical Society, Washington, DC

Halide perovskite solar cells have seen dramatic progress in performance over the past several years. Certified efficiencies of inverted structure (p-i-n) devices have now exceeded 20%. In these p-i-n devices, fullerene compounds are the most popular electron-transfer materials. However, the full function of fullerenes in perovskite solar cells is still under investigation, and the mechanism of photocurrent hysteresis suppression by fullerene remains unclear. In previous reports, thick fullerene layers (>20 nm) were necessary to fully cover the perovskite film surface to make good contact with perovskite film and avoid large leakage currents. In addition, the solution-processed fullerene layer has been broadly thought to infiltrate into the perovskite film to passivate traps on grain boundary surfaces, causing suppressed photocurrent hysteresis. In this work, we demonstrate an efficient perovskite photovoltaic device with only 1 nm C60 deposited by vapor deposition as the electron-selective material. Util...

Visibly transparent luminescent solar concentrators (TLSC) have the potential to turn existing infrastructures into net-zero-energy buildings. However, the reabsorption loss currently limits the device performance and scalability. This loss is typically defined by the Stokes shift between the absorption and emission spectra of luminophores. In this work, the Stokes shifts (SS) of near-infrared selective-harvesting cyanines are altered by substitution of the central methine carbon with dialkylamines. We demonstrate varying SS with values over 80 nm and ideal infrared-visible absorption cutoffs. The corresponding TLSC with such modification shows a power conversion efficiency (PCE) of 0.4% for a >25 cm2 device area with excellent visible transparency >80% and up to 0.6% PCE over smaller areas. However, experiments and simulations show that it is not the Stokes shift that is critical, but the total degree of overlap that depends on the shape of the absorption tails. We show with a series of SS-modulated cyanine dyes that the SS is not necessarily correlated to improvements in performance or scalability. Accordingly, we define a new parameter, the overlap integral, to sensitively correlate reabsorption losses in any LSC. In deriving this parameter, new approaches to improve the scalability and performance are discussed to fully optimize TLSC designs to enhance commercialization efforts.

Inverted perovskite solar cells (PSCs) incorporating poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT) as the hole transport/extraction layer have been broadly investigated in recent years. However, most PSCs which incorporate PEDOT as the hole transport layer (HTL) suffer from lower device performance stemming from reduced photocurrent and low open-circuit voltage around 0.95 V. Here, we report an ultrathin PEDOT layer as the HTL for efficient inverted structure PSCs. The transparency, conductivity, and resulting film morphology were studied and compared with traditional architectures and thicker PEDOT layers. The PSC device incorporating an ultrathin PEDOT layer shows significant improvement in short-circuit current density (JSC), open-circuit voltage (VOC), and power conversion efficiency. Because ultrathin PEDOT layers can be easily obtained by dilution, this study suggests a simple way to improve the PSC performance and provide a route to further reduce the fabrication complexity and cost of PSCs.

Halide perovskite solar cells have seen dramatic progress in performance over the past several years. Certified efficiencies of inverted structure (p-i-n) devices have now exceeded 20%. In these p-i-n devices, fullerene compounds are the most popular electron-transfer materials. However, the full function of fullerenes in perovskite solar cells is still under investigation, and the mechanism of photocurrent hysteresis suppression by fullerene remains unclear. In previous reports, thick fullerene layers (20 nm) were necessary to fully cover the perovskite film surface to make good contact with perovskite film and avoid large leakage currents. In addition, the solution-processed fullerene layer has been broadly thought to infiltrate into the perovskite film to passivate traps on grain boundary surfaces, causing suppressed photocurrent hysteresis. In this work, we demonstrate an efficient perovskite photovoltaic device with only 1 nm C

Perovskite semiconductors have emerged as competitive candidates for photovoltaic applications due to their exceptional optoelectronic properties. However, the impact of moisture instability on perovskite films is still a key challenge for perovskite devices. While substantial effort is focused on preventing moisture interaction during the fabrication process, it is demonstrated that low moisture sensitivity, enhanced crystallization, and high performance can actually be achieved by exposure to high water content (up to 25 vol%) during fabrication with an aqueous‐containing perovskite precursor. The perovskite solar cells fabricated by this aqueous method show good reproducibility of high efficiency with average power conversion efficiency (PCE) of 18.7% and champion PCE of 20.1% under solar simulation. This study shows that water–perovskite interactions do not necessarily negatively impact the perovskite film preparation process even at the highest efficiencies and that exposure to high contents of water can actually enable humidity tolerance during fabrication in air.

Although the high efficiencies of perovskite solar cells have attracted the most attention from the photovoltaic community, one of their most attractive attributes is that flexible devices can be prepared by depositing the perovskite on plastic substrates using solution-based processing techniques. Highly flexible devices have the potential to be fabricated through roll-to-roll manufacturing, which is a fast and easy method for light weight thin-film solar cell production. In order to determine the flexibility of these perovskite-based devices, we have carried out fatigue resistance measurements on flexible perovskite solar cells by bending the devices over a cylinder with a 4 mm radius of curvature for up to 2000 cycles. We show that the main reason for the drop in performance of these devices is the formation of cracks in the indium oxide-based transparent conductive electrode. To improve device flexibility, we substituted the metal oxide electrode with a layer of highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The resulting devices were entirely metal oxide free, and displayed power conversion efficiencies as high as 7.6% with very little hysteresis. By comparing the fatigue resistances of these metal oxide-free devices with those of polymer-based solar cells, we were able to evaluate the inherent flexibility of CH3NH3PbI3 films for the first time.

The recent breakthrough of organometal halide perovskites as the light harvesting layer in photovoltaic devices has led to power conversion efficiencies of over 16%. To date, most perovskite solar cells have adopted a structure in which the perovskite light absorber is placed between carrier-selective electron- and hole-transport layers (ETLs and HTLs). Here we report a new type of compact layer free bilayer perovskite solar cell and conclusively demonstrate that the ETL is not a prerequisite for obtaining excellent device efficiencies. We obtained power conversion efficiencies of up to 11.6% and 13.5% when using poly(3-hexylthiophene) and 2,2',7,7'-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9'-spirobifluorene, respectively, as the hole-transport material. This performance is very comparable to that obtained with the use of a ZnO ETL. Impedance spectroscopy suggests that while eliminating the ZnO leads to an increase in contact resistance, this is offset by a substantial decrease in surface recombination.

Recent advances in the development of perovskite solar cells based on CH3NH3PbI3 have produced devices with power conversion efficiencies of >15%. While initial work in this area assumed that the perovskite-based cells required a mesoporous TiO2 support, many recent reports have instead focused on the development of planar heterojunction structures. A better understanding of how both cell architecture and various design parameters (e.g., perovskite thickness and morphology) affect cell performance is needed. Here, we report the fabrication of perovskite solar cells based on a ZnO nanoparticle electron transport layer, CH3NH3PbI3 light absorber, and poly(3-hexylthiophene) (P3HT) hole transport layer. We show that vapor-phase deposition of the PbI2 precursor film produces devices with performances equivalent to those prepared using entirely solution-based techniques, but with very precise control over the thickness and morphology of the CH3NH3PbI3 layer. Optimization of the layer thickness yielded devices with efficiencies of up to 11.3%. The results further demonstrate that a delicate balance between light absorption and carrier transport is required in these planar heterojunction devices, with the thickest perovskite films producing only very low power conversion efficiencies.

The use of a thin layer of zinc oxide nanoparticles as an electron-transport layer allows flexible perovskite solar cells to be fabricated with a power conversion efficiency as high as 15.7%.

Cyanobacteria (blue-green algae) play profound roles in ecology and biogeochemistry. One model cyanobacterial species is the unicellular cyanobacterium Synechocystis sp. PCC 6803. This species is highly amenable to genetic modification. Its genome has been sequenced and many systems biology and molecular biology tools are available to study this bacterium. Recently, researchers have put significant efforts into understanding and engineering this bacterium to produce chemicals and biofuels from sunlight and CO2. To demonstrate our perspective on the application of this cyanobacterium as a photosynthesis-based chassis, we summarize the recent research on Synechocystis 6803 by focusing on five topics: rate-limiting factors for cell cultivation; molecular tools for genetic modifications; high-throughput system biology for genome wide analysis; metabolic modeling for physiological prediction and rational metabolic engineering; and applications in producing diverse chemicals. We also discuss the particular challenges for systems analysis and engineering applications of this microorganism, including precise characterization of versatile cell metabolism, improvement of product rates and titers, bioprocess scale-up, and product recovery. Although much progress has been achieved in the development of Synechocystis 6803 as a phototrophic cell factory, the biotechnology for “Compounds from Synechocystis” is still significantly lagging behind those for heterotrophic microbes (e.g., Escherichia coli).

Most previous fiber-shaped solar cells were based on photoelectrochemical systems involving liquid electrolytes, which had issues such as device encapsulation and stability. Here, we deposited classical semiconducting polymer-based bulk heterojunction layers onto stainless steel wires to form primary electrodes and adopted carbon nanotube thin films or densified yarns to replace conventional metal counter electrodes. The polymer-based fiber cells with nanotube film or yarn electrodes showed power conversion efficiencies in the range 1.4% to 2.3%, with stable performance upon rotation and large-angle bending and during long-time storage without further encapsulation. Our fiber solar cells consisting of a polymeric active layer sandwiched between steel and carbon electrodes have potential in the manufacturing of low-cost, liquid-free, and flexible fiber-based photovoltaics.

Pt is a classical catalyst that has been extensively used in fuel cell and solar cell electrodes, owing to its high catalytic activity, good conductivity, and stability. In conventional fiber-shaped solar cells, solid Pt wires are usually adopted as the electrode material. Here, we report a Pt nanoparticle-adsorbed carbon nanotube yarn made by solution adsorption and yarn spinning processes, with uniformly dispersed Pt nanoparticles through the porous nanotube network. We have fabricated TiO(2)-based dye-sensitized fiber solar cells with a Pt-nanotube hybrid yarn as counter electrode and achieved a power conversion efficiency of 4.85% under standard illumination (AM1.5, 100 mW/cm(2)), comparable to the same type of fiber cells with a Pt wire electrode (4.23%). Adsorption of Pt nanoparticles within a porous nanotube yarn results in enhanced Pt-electrolyte interfacial area and significantly reduced charge-transfer resistance across the electrolyte interface, compared to a pure nanotube yarn or Pt wire. Our porous Pt-nanotube hybrid yarns have the potential to reduce the use of noble metals, lower the device weight, and improve the solar cell efficiency.

A novel one-dimensional coordination polymeric structure comprised of dinuclear metallorings connected by ligands has been rationally assembled by the reaction of europium nitrate and an amide type bridging podand, 1,3-bis{[(2′-benzylaminoformyl)phenoxyl]methyl}benzene (L). At the same time, the luminescent properties of the Eu(III) complex were also investigated. Under the UV excitation, the complex exhibited characteristic emissions of europium ion and could be significant in the field of supramolecular photonic devices. The triplet excited state T1 of the ligand is well placed to allow energy transfer to Eu3+ excited states.

Solid complexes of terbium, neodymium and yttrium nitrates with an amide type ligand, N-benzyl-2-(benzyloxy)benzamide (L) have been prepared in ethyl acetate and characterized by elemental analysis and IR spectroscopy. The crystal and molecular structures of the complexes TbL3(NO3)3, NdL3(NO3)3 and YL3(NO3)3 have been determined by single crystal X-ray diffraction. The crystal structures of the complexes are similar. The structures show that the crystal consists of two similar but independent molecules in the asymmetric unit and the metal ion is coordinated toward nine donor atoms, three of which belong to the oxygen atoms of three monodentate ligands and six oxygen atoms from three bidentate nitrates. Furthermore, the REL3(NO)3 complex units are linked by the intermolecular hydrogen bonds to form a three-dimensional net. At the same time, the luminescent properties of the ligand and the complex TbL3(NO3)3 were studied as well.

Solar cells based on CH3NH3PbI3 have recently emerged at the forefront of solution-processable photovoltaic devices, with power conversion efficiencies as high as 20.1% having now been certified. In this presentation, I will discuss our research group’s work in the area of perovskite solar cells. Our early work demonstrated that room temperature solution-processing techniques can be used to prepare devices on flexible substrates while retaining excellent power conversion efficiencies. Since then, we have examined issues related to charge carrier diffusion, interfacial contacts, and device flexibility, with our most recent efforts focusing on probing device failure mechanisms using in situ synchrotron-based techniques.

A novel luminescent chemosensor for detecting Hg(2+) with high selectivity, based on a pendant benzo crown ether terbium complex, has been designed and prepared.

A single-layer graphene sheet represents the thinnest transparent conductive electrode for planar photovoltaic devices on both rigid and flexible substrates. Here, we demonstrate fiber-shaped polymer solar cells wrapped by a Au nanoparticle-adsorbed graphene single-layer sheet as a counter electrode, and show cell efficiencies up to 2.53% under standard illumination, which can be improved to 4.36% when tested on a diffusive reflector. This is a relatively high efficiency reported for fiber solar cells using solid-state polymers as active layers. The graphene layer not only serves as a transparent flexible electrode for the fiber solar cells, but also provides good encapsulation on the polymer layers, resulting in excellent flexibility and device stability in both inertial gas and ambient atmosphere, with less than 5% efficiency degradation in air after 8 days. Single-layer graphene is a potential electrode material for constructing efficient and stable polymer fiber solar cells.