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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.

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

Inorganic lead halide perovskite materials have attracted great attention recently due to their potential for greater thermal stability compared to hybrid organic perovskites. However, the high processing temperature to convert from the non-perovskite phase to cubic perovskite phase in many of these systems has limited their application in flexible optoelectronic devices. Here, we report a room temperature processed inorganic PSC based on CsPbI2Br as the light harvesting layer. By combing this composition with key precursor solvents, we show that the inorganic perovskite film can be prepared by the vacuum-assist method under room temperature conditions in air. Unencapsulated devices achieved the power conversion efficiency up to 8.67% when measured under 1-sun irradiation. Exploiting this room temperature process, flexible inorganic PSCs based on an inorganic metal halide perovskite material is demonstrated., Comment: 23 pages, 4 figures, and supplemental information

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.

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.

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.

Perovskite solar cells have recently seen rapid improvements in performance with certified efficiencies of above 23%. Fullerene compounds are a very popular electron-transfer material in these devices. In a previous report, it has been shown that while an ultrathin fullerene layer of just 1 nm is sufficient to achieve good device performance, removal of this layer causes a drastic decrease in performance. We provide an explanation to these observed effects by use of a numerical device model. This work provides theoretical support to the experimental understanding of the dominant role of fullerenes in perovskite solar cells.