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Summary Stacking perovskite solar cells onto crystalline silicon bottom cells in a monolithic tandem configuration enables power-conversion efficiencies (PCEs) well above those of their single-junction counterparts. However, state-of-the-art wide-band-gap perovskite films suffer from phase stability issues. Here, we show how carbazole as an additive to the perovskite precursor solution can not only reduce nonradiative recombination losses but, perhaps more importantly, also can suppress phase segregation under exposure to moisture and light illumination. This enables a stabilized PCE of 28.6% (independently certified at 28.2%) for a monolithic perovskite/silicon tandem solar cell over ∼1 cm2 and 27.1% over 3.8 cm2, built from a textured silicon heterojunction solar cell. The modified tandem devices retain ∼93% of their performance over 43 days in a hot and humid outdoor environment of almost 100% relative humidity over 250 h under continuous 1-sun illumination and about 87% during a 85/85 damp-heat test for 500 h, demonstrating the improved phase stability.

Perovskite/silicon tandem solar cells are emerging as a high-efficiency and prospectively cost-effective solar technology with great promise for deployment at the utility scale. However, despite the remarkable performance progress reported lately, assuring sufficient device stability-particularly of the perovskite top cell-remains a challenge on the path to practical impact. In this work, we analyze the outdoor performance of encapsulated bifacial perovskite/silicon tandems, by carrying out field-testing in Saudi Arabia. Over a six month experiment, we find that the open circuit voltage retains its initial value, whereas the fill factor degrades, which is found to have two causes. A first degradation mechanism is linked with ion migration in the perovskite and is largely reversible overnight, though it does induce hysteretic behavior over time. A second, irreversible, mechanism is caused by corrosion of the silver metal top contact with the formation of silver iodide. These findings provide directions for the design of new and more stable perovskite/silicon tandems

Perovskite/silicon tandem solar cells promise power conversion efficiencies beyond the Shockley–Queisser limit of single-junction devices; however, their actual outdoor performance is yet to be investigated. Here we fabricate 25% efficient two-terminal monolithic perovskite/silicon tandem solar cells and test them outdoors in a hot and sunny climate. We find that the temperature dependence of both the silicon and perovskite bandgaps—which follow opposing trends—shifts the devices away from current matching for two-terminal tandems that are optimized at standard test conditions. Consequently, we argue that the optimal perovskite bandgap energy at standard test conditions is

The metal lead is an integral part of mainstream perovskite solar cells. Lead-based compounds in the form of lead-based paint and lead-contaminated dust are known to potentially trigger long lastin...

Perovskite/silicon tandem solar cells promise power conversion efficiencies (PCE) beyond the thermodynamic limit of single-junction devices. This potential has been unveiled via several champion devices, however, their actual outdoor performance is yet to be investigated. Here, we fabricate 25 %-efficient two-terminal (2T) monolithic perovskite/silicon tandem solar cells and test them outdoors to reveal the characteristics of these devices specifically in hot and sunny climates, which are the ideal locations to operate such efficient photovoltaic devices. In this article, we summarize our observation on the perovskite/silicon tandem solar cells under actual operational conditions and discuss the lessons we take from our interpretations.

A critical bottleneck for improving the performance of organic solar cells (OSC) is minimising non-radiative losses in the interfacial charge-transfer (CT) state via the formation of hybrid energetic states. This requires small energetic offsets often detrimental for high external quantum efficiency (EQE). Here, we obtain OSC with both non-radiative voltage losses (0.24 V) and photocurrent losses (EQE > 80%) simultaneously minimised. The interfacial CT states separate into free carriers with ≈40-ps time constant. We combine device and spectroscopic data to model the thermodynamics of charge separation and extraction, revealing that the relatively high performance of the devices arises from an optimal adjustment of the CT state energy, which determines how the available overall driving force is efficiently used to maximize both exciton splitting and charge separation. The model proposed is universal for donor:acceptor (D:A) with low driving forces and predicts which D:A will benefit from a morphology optimization for highly efficient OSC., Understanding the mechanism of non-radiative losses in organic photovoltaics is crucial to improve the performance further. Here, the authors use combined device and spectroscopic data to reveal universal model to maximise exciton splitting and charge separation by adjusting the energy of charge transfer state.

Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo—the diffuse reflected light from the environment—to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm–2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance. Bifacial solar cells can outperform monofacial cells by exploiting sunlight reflected off the ground surface. De Bastiani et al. show that bifacial perovskite/silicon tandem with an optimized bandgap can deliver a power density of 26 mW cm–2 and compare its performance to monofacial cells under outdoor conditions.

The Cluster of Excellence funded this work through “Engineering of Advanced Materials” (EAM). The authors acknowledge financial support from the DFG research-training group GRK 1896 at Erlangen University and from the Joint Project Helmholtz-Institute Erlangen Nurnberg (HI-ERN) under project number DBF01253, respectively. The authors would like to acknowledge the company rent a scientist (RAS) for material support. C.J.B. acknowledges the financial support through the “Aufbruch Bayern” initiative of the state of Bavaria (EnCN and Solar Factory of the Future) and the “Solar Factory of the Future” with the Energy Campus Nurnberg (EnCN). C.O.R.Q would like to acknowledge Dr. Ning Li, Yi Hou, K. Ding, A. Richter, W. Duan and Andrej Classen for their support during the early stages of this project. Similarly C.O.R.Q would like to acknowledge Sara Mashhoun and Helena Waldau for her helpful advice and graphic design, respectively. A.H-B would like to thank C. Yi for his contributions in checking the electrical characteristics of the silicon solar cell. C.O.R.Q would like to gratefully acknowledge the financial support from The Mexican National Council for Science and Technology (CONACYT). This work was partly supported by the Australian Government through the Australian Renewable Energy Agency (ARENA).

The transfer from poly-3hexylthiophene (P3HT) based fullerene free organic photovoltaic (OPV) lab cells with IDTBR (rhodanine-benzothiadiazole-coupled indacenodithiophene) as acceptor material to fully solution processed roll-to-roll (R2R) compatible modules is reported. The developed R2R process is fully compatible with industrial requirements as it uses exclusively non-hazardous solvents. The combination of optimized ink formulation, module layout, and processing affords efficiencies of 5% on 60 cm2 total module area.

A theoretical understanding of the microstructure of organic semiconducting polymers and blends is vital to further advance the optoelectronic device performance of organic electronics. We outline the theoretical framework of a combined numerical approach based on polymeric solution theory to study the microstructure of polymer:small molecule blends. We feed the results of ab initio density functional theory quantum chemistry calculations into an artificial neural network for the determination of solubility parameters. These solubility parameters are used to calculate Flory–Huggings intermolecular parameters. We further show that the theoretical values are in line with experimentally determined data. On the basis of the Flory–Huggings parameters, we establish a figure of merit as a relative metric for assessing the phase diagrams of organic semiconducting blends in thin films. This is demonstrated for polymer:fullerene blend films on the basis of the prototypical polymers poly(3-hexylthiophene-2,5-diyl) (...

A fundamental understanding of the rich electronic structures of electronically doped semiconductor nanocrystals is vital for assessing the utility of these materials for future applications from solar cells to redox catalysis. Here, we examine the use of magnetic circular dichroism (MCD) spectroscopy to probe the infrared localized surface plasmon resonances of p-Cu2–xSe, n-ZnO, and tin-doped In2O3 (n-ITO) nanocrystals. We demonstrate that the MCD spectra of these nanocrystals can be analyzed by invoking classical cyclotron motions of their excess charge carriers, with experimental MCD signs conveying the carrier types (n or p) and experimental MCD intensities conveying the cyclotron splitting magnitudes. The experimental cyclotron splittings can then be used to quantify carrier effective masses (m*), with results that agree with bulk in most cases. MCD spectroscopy thus offers a unique measure of m* in free-standing colloidal semiconductor nanocrystals, raising new opportunities to investigate the influ...

International audience; A novel main-chain polyfullerene, poly[fullerene-alt-2,5-bis(octyloxy)terephthalaldehyde] (PPC4), is investigated for its hypothesized superior morphological stability as an electron-accepting material in organic photovoltaics relative to the widely used fullerene phenyl-C61-butyric acid methyl ester (PCBM). When mixed with poly(3-hexylthiophene-2,5-diyl) (P3HT), PPC4 affords low-charge-generation yields because of poor intermixing within the blend. The adoption of a multiacceptor system, by introducing PCBM into the P3HT:polyfullerene blend, was found to lead to a 3-fold enhancement in charge generation, affording power conversion efficiencies very close to that of the prototypical P3HT:PCBM binary control. Upon thermal stressing and in contrast to the P3HT:PCBM binary, photovoltaic devices based on the multiacceptor system demonstrated significantly improved stability, outperforming the control because of suppression of the PCBM migration and aggregation processes responsible for rapid device failure. We rationalize the influence of the fullerene miscibility and its implications on the device performance in terms of a thermodynamic model based on Flory-Huggins solution theory. Finally, the potential universal applicability of this approach for thermal stabilization of organic solar cells is demonstrated, utilizing an alternative low-band-gap polymer-donor system

Conjugated polymer semiconductors offer unique advantages over conventional semiconductors but tend to suffer from electro-optic performance roll-off, mainly due to reduced photofastness. Here, we demonstrate that the commodity nickel chelate nickel(II) dibutyldithiocarbamate, Ni(dtc)2, effectively inhibits photooxidation across a wide range of prototypical π-conjugated polymer semiconductors and blends. The addition of 2–10 wt% of Ni(dtc)2 increases the resilience of otherwise quickly photobleaching semiconducting thin films, even in the presence of detrimental, radical forming processing additives. Using electron spin resonance spectroscopy and sensitive oxygen probes, we found that Ni(dtc)2 acts as a broadband stabilizer that inhibits both the formation of reactive radicals and singlet oxygen. The mechanism of stabilization is of sacrificial nature, but contains non-sacrificial contributions in polymers where singlet oxygen is a key driver of photooxidation. Ultrafast pump–probe spectroscopy reveals quenching of triplet excited states as the central mechanism of non-sacrificial stabilization. When introduced into the active layer of organic photovoltaic devices, Ni(dtc)2 retards the short circuit current loss in air without affecting the sensitive morphology of bulk heterojunctions and without major sacrifices in semiconductor properties. Antioxidants based on nickel complexes thus constitute functional stabilizers for elucidating degradation mechanisms in organic semiconductors and represent a cost-effective route toward organic electronic appliances with extended longevity.

Ternary blends with broad spectral absorption have the potential to increase charge generation in organic solar cells but feature additional complexity due to limited intermixing and electronic mismatch. Here, a model system comprising the polymers poly[5,5-bis(2-butyloctyl)-(2,2-bithiophene)-4,4-dicarboxylate-alt-5,5-2,2-bithiophene] (PDCBT) and PTB7-Th and PC70BM as an electron accepting unit is presented. The power conversion efficiency (PCE) of the ternary system clearly surpasses the performance of either of the binary systems. The photophysics is governed by a fast energy transfer process from PDCBT to PTB7-Th, followed by electron transfer at the PTB7-Th:fullerene interface. The morphological motif in the ternary blend is characterized by polymer fibers. Based on a combination of photophysical analysis, GIWAXS measurements and calculation of the intermolecular parameter, the latter indicating a very favorable molecular affinity between PDCBT and PTB7-Th, it is proposed that an efficient charge generation mechanism is possible because PTB7-Th predominantly orients around PDCBT filaments, allowing energy to be effectively relayed from PDCBT to PTB7-Th. Fullerene can be replaced by a nonfullerene acceptor without sacrifices in charge generation, achieving a PCE above 11%. These results support the idea that thermodynamic mixing and energetics of the polymer-polymer interface are critical design parameter for realizing highly efficient ternary solar cells with variable electron acceptors.

The Cluster of Excellence funded this work through “Engineering of Advanced Materials” (EAM). The authors acknowledge financial support from the DFG research-training group GRK 1896 at Erlangen University and from the Joint Project Helmholtz-Institute Erlangen Nurnberg (HI-ERN) under Project No. DBF01253, respectively. C.J.B. acknowledges the financial support through the “Aufbruch Bayern” initiative of the state of Bavaria (EnCN and Solar Factory of the Future) and the “Solar Factory of the Future” with the Energy Campus Nurnberg (EnCN). S.L. acknowledges the Real Colegio Complutense in Harvard for a research grant, and to the Spanish Ministerio de Ciencia e Innovacion for a fellowship through the Salvador de Madariaga Program. L.M.R. and A.A.-G. acknowledge support from Tata Sons Limited – Alliance Agreement (A32391). The computations in this paper were done on the Odyssey cluster supported by the FAS Division of Science, Research Computing Group at Harvard University, and on the Arran cluster supported by the Health Sciences Platform (HSP) at Tianjin University. C.O.R.Q. would like to acknowledge M. Mohrensen for his assistance in graphic design. Similarly, C.O.R.Q. would like to acknowledge Gebhard Matt and Ievgen Levchuk for helpful discussion. G.A. thanks support by the European Research Council (ERC Starting Grant 804110), the Spanish MINECO through the Excellence Unit Maria de Maeztu (MDM-2015-0538), the Generalitat Valenciana (CIDEGENT/2018/001), and the Deutsche Forschungsgemeinschaft (DFG; FLAG-ERA AB694/2-1). G.A. would like to acknowledge Vicent Lloret for his assistance with the experimental work. B. R., L.K., S.A., and G.C. acknowledge support from BMWi through the “PersiST” project (Grant No. 0324037C). S.A. acknowledges funding by the BMBF within the project “Materialforschung fur die Energiewende” for his Young Investigator Group (Grant No. 03SF0540). T.A. gratefully acknowledges the financial support of the Solar Technologies go Hybrid (SolTech) and Bavarian Equal Opportunities Sponsorship – Forderung von Frauen in Forschung und Lehre (FFL). T.U. and M.B. gratefully acknowledge the funding of the German Federal Ministry of Education and Research (BMBF, Project No. 05K16WEB). C.O.R.Q. would like to gratefully acknowledge the financial support from The Mexican National Council for Science and Technology (CONACYT). C.O.R.Q. wrote the manuscript with comments from all coauthors and highlighted contributions from M.S. C.O.R.Q. coordinated and performed photovoltaic device fabrication. C.O.R.Q. coordinated all experiments, measurements, and simulations. G.D.S. assisted with the tandem lamination process. C.O.R.Q. and K.F. performed optical simulations. M.S., G.D.S., N.L., T.A., and A.A.-G. assisted with data interpretation, story layout design, and contributed ideas. C.O.R.Q., N.S., and E.S. contributed with the electron microscopy analysis. C.O.R.Q., M.B., and T.B. contributed with X-ray studies. C.O.R.Q., G.A., F.H., and A.H. contributed with Raman studies. L.-I.D.-B., and N.G. assisted with PL measurements. N.G. and A.C. assisted with FTPS and PL data analysis and interpretation. M.M., G.C., L.K., B.R., and S.A. provided silicon cells. QM/DFT calculations and analysis were performed by L.M.R. MD parametrization was done by S.L., and MD simulations were performed and analyzed by S.L. and J.D.P. C.J.B. supervised the project.

We demonstrate an innovative solution-processing fabrication route for organic and perovskite solar modules via depth-selective laser patterning of an adhesive top electrode. This yields unprecedented power conversion efficiencies of up to 5.3% and 9.8%, respectively. We employ a PEDOT:PSS–Ag nanowire composite electrode and depth-resolved post-patterning through beforehand laminated devices using ultra-fast laser scribing. This process affords low-loss interconnects of consecutive solar cells while overcoming typical alignment constraints. Our strategy informs a highly simplified and universal approach for solar module fabrication that could be extended to other thin-film photovoltaic technologies.

Fullerene dimerization has been linked to short circuit current (Jsc) losses in organic solar cells comprised of certain polymer–fullerene systems. We investigate several polymer–fullerene systems, which present Jsc loss to varying degrees, in order to determine under which conditions dimerization occurs. By reintroducing dimers into fresh devices, we confirm that the photo-induced dimers are indeed the origin of the Jsc loss. We find that both film morphology and electrical bias affect the photodimerization process and thus the associated loss of Jsc. In plain fullerene films, a higher degree of crystallinity can inhibit the dimerization reaction, as observed by high performance liquid chromatography (HPLC) measurements. In blend films, the amount of dimerization depends on the degree of mixing between polymer and fullerene. For highly mixed systems with very amorphous polymers, no dimerization is observed. In solar cells with pure polymer and fullerene domains, we tune the fullerene morphology from amorphous to crystalline by thermal annealing. Similar to neat fullerene films, we observe improved light stability for devices with crystalline fullerene domains. Changing the operating conditions of the investigated solar cells from Voc to Jsc also significantly reduces the amount of dimerization-related Jsc loss; HPLC analysis of the active layer shows that more dimers are formed if the cell is held at Voc instead of Jsc. The effect of bias on dimerization, as well as a clear correlation between PL quenching and reduced dimerization upon addition of small amounts of an amorphous polymer into PC60BM films, suggests a reaction mechanism via excitons.

Correction for ‘Balancing electrical and optical losses for efficient 4-terminal Si-perovskite solar cells with solution processed percolation electrodes’ by César Omar Ramírez Quiroz et al., J. Mater. Chem. A, 2018, 6, 3583–3592.

The photovoltaic performance and optoelectronic properties of a donor–acceptor copolymer are reported based on indacenodithienothiophene (IDTT) and 2,3-bis(3-(octyloxy)phenyl)quinoxaline moieties (PIDTTQ) as a function of the number-average molecular weight (Mn). Current–voltage measurements and photoinduced charge carrier extraction by linear increasing voltage (photo-CELIV) reveal improved charge generation and charge transport properties in these high band gap systems with increasing Mn, while polymers with low molecular weight suffer from diminished charge carrier extraction because of low mobility–lifetime (μτ) product. By combining Fourier-transform photocurrent spectroscopy (FTPS) with electroluminscence spectroscopy, it is demonstrate that increasing Mn reduces the nonradiative recombination losses. Solar cells based on PIDTTQ with Mn = 58 kD feature a power conversion efficiency of 6.0% and a charge carrier mobility of 2.1 × 10−4 cm2 V−1 s−1 when doctor bladed in air, without the need for thermal treatment. This study exhibits the strong correlations between polymer fractionation and its optoelectronics characteristics, which informs the polymer design rules toward highly efficient organic solar cells.

Photovoltaic devices based on organic semiconductors (OPVs) hold great promise as a cost-effective renewable energy platform because they can be processed from solution and deposited on flexible plastics using roll-to-roll processing. Despite important progress and reported power conversion efficiencies of more than 10% the rather limited stability of this type of devices raises concerns towards future commercialization. The tandem concept allows for both absorbing a broader range of the solar spectrum and reducing thermalization losses. We designed an organic tandem solar cell with an inverted device geometry comprising environmentally stable active and charge-selecting layers. Under continuous white light irradiation, we demonstrate an extrapolated, operating lifetime in excess of one decade. We elucidate that for the current generation of organic tandem cells one critical requirement for long operating lifetimes consists of periodic UV light treatment. These results suggest that new material approaches towards UV-resilient active and interfacial layers may enable efficient organic tandem solar cells with lifetimes competitive with traditional inorganic photovoltaics.

While perovskite-based semitransparent solar cells deliver competitive levels of transparency and efficiency to be envisioned for urban infrastructures, the complexity and sensitivity of their processing conditions remain challenging. Here, we introduce two robust protocols for the processing of sub-100 nm perovskite films, allowing fine-tuning of the active layer without compromising the crystallinity and quality of the semiconductor. Specifically, we demonstrate that a method based on solvent-induced crystallization with a rapid drying step affords perovskite solar cells with 37% average visible transmittance (AVT) and 7.8% PCE. This process enhances crystallization with a preferential phase orientation presumably at the interface, yielding a high fill factor of 72.3%. The second method is based on a solvent–solvent extraction protocol, enabling active layer films as thin as 40 nm and featuring room-temperature crystallization in an ambient environment on a few second time span. As a result, we demonstrate a maximum AVT of 46% with an efficiency of 3.6%, which is the highest combination of efficiency and transparency for a full device stack to date. By combining the two methods presented here we cover a broad range of thicknesses vs. transparency values and confirm that solvent-induced crystallization represents a powerful processing strategy toward high-efficiency semitransparent solar cells. Optical simulations support our experimental findings and provide a global perspective of the opportunities and limitations of semitransparent perovskite photovoltaic devices.

We present a novel ternary organic solar cell with an uncommonly thick active layer (similar to 300 nm), featuring thickness invariant charge carrier recombination and delivering 11% power conversion efficiency (PCE). A ternary blend was used to demonstrate photovoltaicmodules of high technological relevance both on glass and flexible substrates, yielding 8.2% and 6.8% PCE, respectively.

We investigate the effect of quantum dot size on photocurrent and photoinduced charge transfer yields in blends of the conjugated polymer, poly((4,8-bis(octyloxy)benzo(1,2-b:4,5-b′)dithiophene-2,6-diyl)(2-((dodecyloxy)carbonyl)thieno(3,4-b)thiophenediyl)) (PTB1), with PbS nanocrystal quantum dots (QDs). These hybrid solar cells exhibit external quantum efficiencies of over 70% and power conversion efficiencies of up to 2.8%. We use photoinduced absorption (PIA) spectroscopy and device EQE measurements to probe long-lived charge transfer at the polymer/QD interface as a function of QD size. We observe that both the PIA signal associated with charge formation on the polymer, as well as the external quantum efficiency of the hybrid photovoltaic devices decrease in magnitude with increasing quantum dot size, despite the broader absorption spectrum of the larger dots. We interpret these results as evidence that PTB1/PbS blends behave at least partially as bulk heterojunction (BHJ) solar cells, and conclude tha...

Organic solar cell technology bears the potential for high photovoltaic performance combined with truly low-cost, high-volume processing. Here we demonstrate organic tandem solar modules on flexible substrates fabricated by fully roll-to-roll compatible processing at temperatures

An all-solid-state quantum-dot-based photon-to-current conversion device is demonstrated that selectively detects the generation of hot electrons. Photoexcitation of Mn

While the development of perovskite-based semitransparent solar cells with competitive levels of transparency and efficiency offer a promising perspective towards building integrated photovoltaics, the color perception of perovskite films is of limited visual aesthetics, compromising their applicability to facades and windows. In the present work, we develop a technique to grow crystalline, ultrathin perovskite films through a solvent-solvent extraction process featuring full crystallization within few seconds at RT and under 45%RH environmental conditions. As a result we obtained the highest combination of efficiency and transparency to date for perovskite solar cells. We further improved the visual aesthetics of our devices by implementing dielectric mirrors. EQE and UV-Vis spectroscopic measurements are performed to fully characterize the device stacks featuring four different dielectric mirror configurations. By customizing the mirror to the near-IR absorption region of the perovskite, we could increase the Jsc by 18.7%, yielding a light blue appearance and showing 31.4% transparency at 3.5% electrical power efficiency. Both, the solar cells and the dielectric mirrors are fully-solution processed under ambient conditions and are easily transferable to roll-to-roll upscaling. Optical simulations support our experimental findings and provide a global perspective emulating full device stack appearance covering all the colors in the visible spectra. Transparency, photocurrent density contribution and chromaticity are finally simulated and analyzed. Based on the detailed analysis, we give an outlook on the performance – color – transparency roadmap for perovskite solar cells.

The solubility of organic semiconductors in environmentally benign solvents is an important prerequisite for the widespread adoption of organic electronic appliances. Solubility can be determined by considering the cohesive forces in a liquid via Hansen solubility parameters (HSP). We report a numerical approach to determine the HSP of fullerenes using a mathematical tool based on artificial neural networks (ANN). ANN transforms the molecular surface charge density distribution (σ-profile) as determined by density functional theory (DFT) calculations within the framework of a continuum solvation model into solubility parameters. We validate our model with experimentally determined HSP of the fullerenes C60, PC61BM, bisPC61BM, ICMA, ICBA, and PC71BM and through comparison with previously reported molecular dynamics calculations. Most excitingly, the ANN is able to correctly predict the dispersive contributions to the solubility parameters of the fullerenes although no explicit information on the van der Waals forces is present in the σ-profile. The presented theoretical DFT calculation in combination with the ANN mathematical tool can be easily extended to other π-conjugated, electronic material classes and offers a fast and reliable toolbox for future pathways that may include the design of green ink formulations for solution-processed optoelectronic devices.

International audience; The first oligomerisation of phenyl-C61-butyric acid methyl ester (PCBM) using a facile atom transfer radical addition polymerization (ATRAP) and its exploitation for organic photovoltaic devices is described. Oligo\(phenyl-C61-butyric acid methyl ester)-alt-[1,4-bis(bromomethyl)-2,5-bis(octyloxy)benzene]\ (OPCBMMB) shows opto-electronic properties equivalent to those of PCBM but has a higher glass transition temperature. When mixed with various band gap semiconducting polymers, OPCBMMB delivers performances similar to PCBM but with an enhanced stabilization of the bulk heterojunction in photovoltaic devices on plastic substrates under thermal stress, regardless of the degree of crystallinity of the polymer and without changing opto-electronic properties. © 2016 The Royal Society of Chemistry.

Plasmonic metal nanoparticles have been used to enhance the performance of thin-film devices such as organic photovoltaics based on polymer/fullerene blends. We show that silver nanoprisms accumulate long-lived negative charges when they are in contact with a photoexcited bulk heterojunction blend composed of poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM). We report both the charge modulation and electroabsorption spectra of silver nanoprisms in solid-state devices and compare these spectra with the photoinduced absorption spectra of P3HT/PCBM blends containing silver nanoprisms. We assign a previously unidentified peak in the photoinduced absorption spectra to the presence of photoinduced electrons on the silver nanoprisms. We show that coating the nanoprisms with a 2.5 nm thick insulating layer can completely inhibit this charging. These results may inform methods for limiting metal-mediated losses in plasmonic solar cells.

Human life requires energy. Moreover, people spend around 90% of their time in buildings while about 40% of primary energy needs are due to buildings. That is why the present paper deals with a methodology allowing identifying and assessing the energy impact of a building on the electricity grid. Thanks to both the building models we developed and fuzzy logic contribution (used to control ventilation and develop occupancy scenarios related to human habits and lifestyle), the results we obtained in simulation validate the proposed impact indicator. Different insulation levels were considered as well as energy production (solar photovoltaic and thermal panels and a vertical axis windmill) and storage (a domestic hot water tank) systems. These results highlighted the pertinence of such an indicator for optimizing the design of the just-mentioned systems and minimizing the amount of energy exchanged by buildings and the electricity grid. One can promote energy injection or take into account the status of the electricity grid when designing these systems. As a key result, the produced renewable energy is partially self-consumed, what allows for a more efficient and rational use of energy in buildings.

Resonance Raman spectra have been obtained for the organic solar cell blend poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester (P3HT/PCBM) at excitation wavelengths ranging from 364 to 633 nm, in both the presence and absence of triangular Ag nanoprisms with varying plasmon resonance frequencies. For ∼35 nm polymer films deposited over nanoprisms, the nanoprisms enhance the sample-averaged Raman scattering intensities by factors of 2–20 depending on wavelength and nanoprism density. The weak blend fluorescence is enhanced by approximately the same factor as the Raman scattering, implying negligible excited-state quenching by the metal. The Raman peak positions and relative intensities are unaffected by the nanoprisms, indicating negligible morphological or chemical changes to the P3HT. The observed Raman enhancements are qualitatively consistent with previously observed enhancements in charge-carrier (positive polaron) yields for P3HT/PCBM deposited over silver nanoprisms.

This review describes recent advances and applications in the field of organic photorefractive materials, an interesting area in the field of organic electronics and promising candidate for various aspects of photonic applications. We describe the current state of knowledge about the processes involved in the formation of photorefractive gratings in organic materials and focus on the chemical and photo-physical aspects of the material structures employed in low glass-transition temperature amorphous composites and organic photorefractive glasses. State-of-the art materials are highlighted and recent demonstrations of photonic applications relying on the reversible holographic nature of the photorefractive materials are discussed.

This essay offers the weyekin principle to address the symbol–material, human–nature dualisms found in much of our theory and critiqued by a growing number of environmental communication scholars. The authors see two core requirements for transforming our engagement with the nonhuman: first, a way of attending to or interpreting natural phenomena that opens our awareness to other-than-symbolic modes of experience; and second, an embodied critique that expresses the inherent tensions of the symbolic–material interface.

When released, The Day After Tomorrow was widely described by critics and the movie's creators as a pro-environmentalist film. This essay argues that The Day After Tomorrow articulates a variation of apocalyptic discourse identified as a flood myth. The authors conclude that this version of the flood myth largely undermines contemporary environmental discourse that attempts to generate public activism in addressing ecological problems, by replacing an emphasis on human efficacy with symbolic vindication and exchanging collective effort for individual survivalism. The film thus serves as a cautionary tale about the potential consequences of contemporary mythic discourse presented as supporting environmental activism.

The effect of beam walk-off is known to reduce the overlap region of the writing beams in coherence domain holographic imaging. In photorefractive (PR) polymer devices this problem is particularly pronounced because of the restrictions that are imposed by the slanted recording geometry. Here, we demonstrate that by optically demagnifying the image bearing signal beam the field of view can be enhanced by a factor of 8. In addition, we found that the area ratio of the writing and readout beams determines both the PR performance and the depth resolution. In a second approach, we show that by changing the recording geometry from transmission to reflection the field of view can be almost fully recovered.

Herein we document two cases of discrepant typing results obtained when data from both exon 2 and 3 is used to analyze LabType SSO results for HLA-DQ using the HLA Fusion software. The first case is an ASHI PT sample (HT-184) tested by LabType SSO and analyzed using HLA Fusion 4.1. For this sample, 39% of survey participants reported HLA-DQA1*05:05, 26% HLA-DQA1*05:02 and the remaining labs reported either a new allele, HLA-DQA1*05:01G or P. By sequence based analysis (SBT) the correct typing is HLA-DQA1*05:02,*01:01. When using LabType SSO and analyzing with HLA Fusion 4.1, including both exon 2 and 3, the typing obtained is HLA-DQA1*05:05/09/11 when bead #56 is excluded. The software flags bead #56 as a false positive bead. No typing is obtained without excluding bead 56. HLA-DQA1*05:05 was the most common response on the PT survey indicating several labs may be analyzing data using Fusion and excluding bead #56 from the analysis. The correct typing HLA-DQA1*05:02 can only be obtained when HLA-DQA1 exon 3 is excluded from the analysis despite the fact that the probe attached to bead 56 binds to DQA1*05:02 but not DQA1*05:05. The issue encountered with this sample stems from the fact that HLA-DQA1*05:02 does not have an exon 3 sequence in IMGT. As such, the probe pattern for exon 3 has not been established for this allele. The software automatically rules out alleles with no exon 3 sequences from the possible allele string when the analysis includes both exon 2 and 3 rather than flagging it as a possibility and indicating exon 3 sequence is not available for this allele. The second case is a patient typed by SBT as HLA-DQB1*06:11, *03:03. When the sample is tested using LabType SSO and analyzed using HLA Fusion 4.1 the typing obtained is HLA-DQB1*03:03, *06:112 N. The correct typing, HLA-DQB1*03:03, *06:11 can only be obtained when HLA-DQB1 exon 3 data is excluded from the analysis. Again this is because the sequence for exon 3 is not available in IMGT for HLA-DQB1*06:11:01. The two cases presented are representative of others we have encountered and reinforces the importance of software validation in the laboratory. Regardless of vendors and methodologies most software have limitations and impute some HLA typing data. As such, a variety of typing samples with specific allele combinations should be used in validation studies.

We report on a series of near infrared (NIR)-sensitive photorefractive polymer composites (PPCs) based on the hole-conducting polymer PF6-TPD, which are sensitized by soluble fullerene-derivatives as electron-accepting agents. We demonstrate a direct correlation between the electron accepting capability of the sensitizer and the holographic response time. The holographic recording speed is found to improve by one order of magnitude when lowering the reduction potential of the sensitizer by approx. 400 mV, while all other physical parameters of the materials remain essentially identical. Furthermore, the lifetime of the mobile charge carriers is found to correlate linearly with the reduction potential, thus indicating a decrease in recombination rates for stronger accepting capability of the sensitizer. Finally, we found that pre-illumination enhanced the holographic sensitivity. The effect is found to be most pronounced for the strongest acceptor due to reduced recombination of the preformed carriers. Overall, the PPCs reported here feature the currently highest sensitivity in the NIR spectral region.

Photorefractive polymers allow to reversibly record holograms over a broad spectral range. This capability offers the possibility to store the information contained in ultrafast optical pulses (i.e., time domain) in the frequency domain. We demonstrate a storage bandwidth of >80 nm around 800 nm (i.e., >36 THz), giving a temporal resolution for Gaussian pulses of 13 fs at room temperature. Time reversal of a pulse train of 130 fs pulses confirms these capabilities.

The production of high-performance, solution-processed kesterite Cu2ZnSn(Sx,Se1-x)4 (CZTSSe) solar cells typically relies on high-temperature crystallization processes in chalcogen-containing atmosphere and often on the use of environmentally harmful solvents, which could hinder the widespread adoption of this technology. We report a method for processing selenium free Cu2ZnSnS4 (CZTS) solar cells based on a short annealing step at temperatures as low as 350 °C using a molecular based precursor, fully avoiding highly toxic solvents and high-temperature sulfurization. We show that a simple device structure consisting of ITO/CZTS/CdS/Al and comprising an extremely thin absorber layer (∼110 nm) achieves a current density of 8.6 mA/cm(2). Over the course of 400 days under ambient conditions encapsulated devices retain close to 100% of their original efficiency. Using impedance spectroscopy and photoinduced charge carrier extraction by linearly increasing voltage (photo-CELIV), we demonstrate that reduced charge carrier mobility is one limiting parameter of low-temperature CZTS photovoltaics. These results may inform less energy demanding strategies for the production of CZTS optoelectronic layers compatible with large-scale processing techniques.

A facile, high-yield synthesis of edge gold-coated silver nanoprisms (GSNPs) with a gold nanoframe as thin as 1.7 nm and their comprehensive characterizations by using various spectroscopic and microscopic techniques is introduced. The GSNPs exhibit remarkably higher stability than silver nanoprisms (SNPs) and are therefore explored as effective optical antennae for light-harvesting applications. When embedded into a bulk heterojunctions film of P3HT:PCBM, plasmonic GSNPs with a localized surface plasmon resonance (LSPR) around 500 nm can effectively act as optical antennae to enhance light harvesting in the active layer. As a result, we measured up to 7-fold enhancement in the polaron generation yield through photoinduced absorption spectroscopy. Owing to the high stability and strong field enhancement, the presented GSNPs feature great potential as plasmonic probes for photovoltaic applications and LSPR sensing.