28.2%-efficient, outdoor-stable perovskite/silicon tandem solar cell

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

Green Pathways for the Enzymatic Synthesis of Furan-Based Polyesters and Polyamides

The attention towards the utilization of sustainable feedstocks for polymer synthesis has grown exponentially in recent years. One of the spotlighted monomers derived from renewable resources is 2,5-furandicarboxylic acid (FDCA), one of the most promising bio-based monomers, due to its resemblance to petroleum-based terephthalic acid. Very interesting synthetic routes using this monomer have been reported in the last two decades. Combining the use of bio-based monomers and non-toxic chemicals via enzymatic polymerizations can lead to a robust and favorable approach towards a greener technology of bio-based polymer production. In this chapter, a brief introduction to FDCA-based monomers and enzymatic polymerizations is given, particularly focusing on furan-based polymers and their polymerization. In addition, an outline of the recent developments in the field of enzymatic polymerizations is discussed. </p

Review on catalytic cleavage of C-C inter-unit linkages in lignin model compounds: Towards lignin depolymerisation

Lignin depolymerisation has received considerable attention recently due to the pressing need to find sustainable alternatives to fossil fuel feedstock to produce chemicals and fuels. Two types of interunit linkages (C–C and C–O linkages) link several aromatic units in the structure of lignin. Between these two inter-unit linkages, the bond energies of C–C linkages are higher than that of C–O linkages, making them harder to break. However, for an efficient lignin depolymerisation, both types of inter-unit linkages have to be broken. This is more relevant because of the fact that many delignification processes tend to result in the formation of additional C–C inter-unit bonds. Here we review the strategies reported for the cleavage of C–C inter-unit linkages in lignin model compounds and lignin. Although a number of articles are available on the cleavage of C–O inter-unit linkages, reports on the selective cleavage of C–C inter-unit linkages are relatively less. Oxidative cleavage, hydrogenolysis, two-step redox-neutral process, microwave assisted cleavage, biocatalytic and photocatalytic methods have been reported for the breaking of C–C inter-unit linkages in lignin. Here we review all these methods in detail, focused only on the breaking of C–C linkages. The objective of this review is to motivate researchers to design new strategies to break this strong C–C inter-unit bonds to valorise lignins, technical lignins in particular

Biochemical characterization and low-resolution SAXS shape of a novel GH11 exo-1,4-β-xylanase identified in a microbial consortium

Biotechnologies that aim to produce renewable fuels, chemicals, and bioproducts from residual ligno(hemi)cellulosic biomass mostly rely on enzymatic depolymerization of plant cell walls (PCW). This process requires an arsenal of diverse enzymes, including xylanases, which synergistically act on the hemicellulose, reducing the long and complex xylan chains to oligomers and simple sugars. Thus, xylanases play a crucial role in PCW depolymerization. Until recently, the largest xylanase family, glycoside hydrolase family 11 (GH11) has been exclusively represented by endo-catalytic β-1,4- and β-1,3-xylanases. Analysis of a metatranscriptome library from a microbial lignocellulose community resulted in the identification of an unusual exo-acting GH11 β-1,4-xylanase (MetXyn11). Detailed characterization has been performed on recombinant MetXyn11 including determination of its low-resolution small angle Xray scattering (SAXS) molecular envelope in solution. Our results reveal that MetXyn11 is a monomeric globular enzyme that liberates xylobiose from heteroxylans as the only product. MetXyn11 has an optimal activity in a pH range from 6 to 9 and an optimal temperature of 50 oC. The enzyme maintained above 65% of its original activity in the pH range 5 to 6 after being incubated for 72 h at 50 oC. Addition of the enzyme to a commercial enzymatic cocktail (CelicCtec3) promoted a significant increase of enzymatic hydrolysis yields of hydrothermally pretreated sugarcane bagasse (16% after 24 h of hydrolysis)

Molecular engineering of contact interfaces for high-performance perovskite solar cells

Metal-oxide-based charge-transport layers have played a pivotal role in the progress of perovskite solar cells. Yet metal-oxide/perovskite interfaces are often highly defective, owing to both metal-oxide and perovskite surface defects. This results in non-radiative recombination and impedes charge transfer. Moreover, during operation, such interfaces may suffer from undesirable chemical reactions and mechanical delamination issues. Solving this multifaceted challenge requires a holistic approach to concurrently address the interfacial defect, charge-transfer, chemical stability and delamination issues, to bring perovskite solar cell technology closer to commercialization. With this motivation, we review and discuss the issues associated with the metal-oxide/perovskite interface in detail. With this knowledge at hand, we then suggest solutions based on molecular engineering for many, if not all, challenges that encumber the metal-oxide/perovskite interface. Specifically, in light of the semiconducting and ultrafast charge-transfer properties of dyes and the recent success of self-assembled monolayers as charge-selective contacts, we discuss how such molecules can potentially be a promising solution for all metal-oxide/perovskite interface issues

Recombination junctions for efficient monolithic perovskite-based tandem solar cells: Physical principles, properties, processing and prospects

Crystalline silicon (c-Si) solar cells comprise more than 95% of the photovoltaics (PV) market. At wafer-scale, this technology is gradually reaching its practical power conversion efficiency (PCE) limit. Therefore, new performance-driven and scalable alternatives must be developed to further increase the cost-competitiveness of PV. Stacked PV absorbers with decreasing bandgaps in a tandem configuration utilize more efficiently the solar spectrum, and can thereby overcome the single-junction efficiency limit of conventional solar cells. Specifically, the monolithic, two-terminal tandem solar cell implementation promises a simple, yet high-performance technology with high market-relevance. Metal-halide perovskite absorbers have attracted broad interest in their application as the top cell of such a c-Si based tandem solar cell configuration. Practically, the perovskite and c-Si subcells need to be electronically coupled, where the interfacial structure should guarantee efficient charge recombination of majority carriers (collected from each subcell), without inducing minority-carrier recombination. In this article, we review the mechanism underlying efficient recombination junctions, and discuss available materials systems for perovskite-based tandems, as well as additional requirements such as efficient light coupling into the subcells, processing compatibility, scalability of materials and methods, and stability. We extend our discussion beyond c-Si to thin-film bottom cell technologies such as low-bandgap perovskites and chalcogenides. We conclude with an outlook on considerations for industrialization of such interfacial structures. This journal i

Eco-Friendly Spray Deposition of Perovskite Films on Macroscale Textured Surfaces

An innovative sequential eco-friendly spray coating (SEF-SC) technique is developed to uniformly deposit metal halide perovskite films on macroscale textured surfaces, such as textured crystalline-silicon wafers. Contrasting with previous work on spray-coated perovskite solar cells, the method presented in this work completely avoids the use of toxic and dangerous solvents. Both MAPbI3 and CsFAMAPbI3−xBrx perovskite films deposited by SEF-SC show excellent optoelectronic properties and no phase segregation, even when synthesized in ambient conditions. Uniform perovskite coatings are obtained on textured-silicon heterojunction solar cells underlining the promise of this method, which holds the potential for scalable wet processing of perovskites on rough substrates, such as for low-cost perovskite/silicon tandem solar cell fabrication

High-performance perovskite single-junction and textured perovskite/silicon tandem solar cells via slot-die-coating

In this work, we report perovskite solar cells in the planar p-i-n configuration based on single-step, anti-solvent-free, low-temperature (70 °C) slot-die-coated methylammonium lead tri-iodide (MAPbI3). The devices are fabricated on hydrophobic poly(triarylamine) (PTAA) surfaces, using key strategies such as solvent engineering, enhanced ink-substrate dynamics, and surface passivation, enabling a power conversion efficiency (PCE) of 21.8%. We also adapted the technique to achieve the first slot-die-coated perovskite/silicon monolithic 2-terminal tandems, achieving a PCE of 23.8% utilizing a textured silicon bottom cell

Tin Oxide Electron-Selective Layers for Efficient, Stable, and Scalable Perovskite Solar Cells

Perovskite solar cells (PSCs) have become a promising photovoltaic (PV) technology, where the evolution of the electron-selective layers (ESLs), an integral part of any PV device, has played a distinctive role to their progress. To date, the mesoporous titanium dioxide (TiO2)/compact TiO2 stack has been among the most used ESLs in state-of-the-art PSCs. However, this material requires high-temperature sintering and may induce hysteresis under operational conditions, raising concerns about its use toward commercialization. Recently, tin oxide (SnO2) has emerged as an attractive alternative ESL, thanks to its wide bandgap, high optical transmission, high carrier mobility, suitable band alignment with perovskites, and decent chemical stability. Additionally, its low-temperature processability enables compatibility with temperature-sensitive substrates, and thus flexible devices and tandem solar cells. Here, the notable developments of SnO2 as a perovskite-relevant ESL are reviewed with emphasis placed on the various fabrication methods and interfacial passivation routes toward champion solar cells with high stability. Further, a techno-economic analysis of SnO2 materials for large-scale deployment, together with a processing-toxicology assessment, is presented. Finally, a perspective on how SnO2 materials can be instrumental in successful large-scale module and perovskite-based tandem solar cell manufacturing is provided

Photon recycling in perovskite solar cells and its impact on device design

Metal halide perovskites have emerged in recent years as promising photovoltaic materials due to their excellent optical and electrical properties, enabling perovskite solar cells (PSCs) with certified power conversion efficiencies (PCEs) greater than 25%. Provided radiative recombination is the dominant recombination mechanism, photon recycling – the process of reabsorption (and re-emission) of photons that result from radiative recombination – can be utilized to further enhance the PCE toward the Shockley–Queisser (S-Q) theoretical limit. Geometrical optics can be exploited for the intentional trapping of such re-emitted photons within the device, to enhance the PCE. However, this scheme reaches its fundamental diffraction limits at the submicron scale. Therefore, introducing photonic nanostructures offer attractive solutions to manipulate and trap light at the nanoscale via light coupling into guided modes, as well as localized surface plasmon and surface plasmon polariton modes. This review focuses on light-trapping schemes for efficient photon recycling in PSCs. First, we summarize the working principles of photon recycling, which is followed by a review of essential requirements to make this process efficient. We then survey photon recycling in state-of-the-art PSCs and propose design strategies to invoke light-trapping to effectively exploit photon recycling in PSCs. Finally, we formulate a future outlook and discuss new research directions in the context of photon recycling