solar, wind, hydro, geothermal, and biomass, to enable a steady mitigation of greenhouse gas emissions, which are causing the planetary climate change and global warming. [5][6][7] Additionally, due to the economic development and the worldwide urbanization, a continuous rise of the global energy consumption across all key sectors, that is, power, heating, industry, and transport is occurring. This is expressed by an increase in the annual global electricity demand by 4.5% in 2021 corresponding to additional 1000 TWh. [4] Hence, strict criteria for the selection of competitive and abundant energy alternatives are imposed, requiring high yield at affordable prices. [8] The share of total renewables power generation excluding hydropower exceeded 3000 TWh in 2020, corresponding to almost 12% of the global electricity generation. [3] Considering an effective synergy between various sustainable energy candidates, solar photovoltaics (PV) have demonstrated great capabilities that can satisfy the requirements in the pathway towards 100% renewable electricity. [9][10][11][12] Owing to the research and development activities over the last decades, the power conversion efficiencies of solar cells (SC) have skyrocketed with a prolonged operation lifetime (>15 years) and a drastic plummeting in manufacturing costs (global average module selling price below $0.25 per W). [6,[13][14][15] The rapid universal deployment of PV resulted in a contribution of about 3.4% in the worldwide electricity generation in 2020. [3] Presently, the global installed PV capacity is approaching 1 TW and it is envisioned to reach ≈10 TW by 2030 and 30 to 70 TW by 2050. [16] Interestingly, along with massive electricity production using conventional solar power plants and rooftop solar panels, ancillary concepts of PV offer new strategies for supplying modern systems in versatile applications. [17][18][19] Moreover, diverse functionalities beyond solar energy harvesting can be afforded by adaptive PV, including aesthetic appearance, visual comfort and thermal management. [17,18,20,21] The distributed nature and the ubiquitous accessibility of multifunctional PV products are substantial features of solar PV in contrast to other renewable energies. However, traditional SCs dominating the market impose intrinsic optoelectronic and thermomechanical limitations, that prohibit their multifunctional utilization. To overcome these drawbacks, novel functional materials and innovative device architecture Solar photovoltaics (PV) offer viable and sustainable solutions to satisfy the growing energy demand and to meet the pressing climate targets. The deployment of conventional PV technologies is one of the major contributors of the ongoing energy transition in electricity power sector. However, the diversity of PV paradigms can open different opportunities for supplying modern systems in a wide range of terrestrial, marine, and aerospace applications. Such ubiquitous and versatile applications necessitate the development of PV technologies with customized desig...

Melanin is a widely distributed and striking dark-colored pigment produced by countless living organisms. Although a wide range of bioactivities have been recognized, there are still major constraints in using melanin for biotechnological applications such as its fragmentary known chemical structure and its insolubility in inorganic and organic solvents. In this study, a bacterial culture of Streptomyces cavourensis SV 21 produced two distinct forms of melanin: (1) a particulate, insoluble form as well as (2) a rarely observed water-soluble form. The here presented novel, acid-free purification protocol of purified particulate melanin (PPM) and purified dissolved melanin (PDM) represents the basis for an in-depth comparison of their physicochemical and biological properties, which were compared to the traditional acid-based precipitation of melanin (AM) and to a synthetic melanin standard (SM). Our data show that the differences in solubility between PDM and PPM in aqueous solutions may be a result of different adjoining cation species, since the soluble PDM polymer is largely composed of Mg2+ ions and the insoluble PPM is dominated by Ca2+ ions. Furthermore, AM shared most properties with SM, which is likely attributed to a similar, acid-based production protocol. The here presented gentler approach of purifying melanin facilitates a new perspective of an intact form of soluble and insoluble melanin that is less chemical altered and thus closer to its original biological form.

Transition metal dichalcogenides, such as molybdenum disulfide (MoS 2 ), have unique electronic and optoelectronic properties that are often altered by environmental effects, particularly substrate or contact materials. Understanding these effects is important for device design and engineering. There is limited information concerning how MoS 2 interacts with 3D semiconductors such as metal oxides. This work demonstrates the influence of substrate material and MoS 2 layer thickness on the work function of exfoliated MoS 2 flakes. Kelvin probe force microscopy is used to probe the work function of MoS 2 on titanium oxide (TiO x ), molybdenum oxide (MoO x ), and gold (Au). We find that TiO x based substrates yield a lower MoS 2 work function than MoO x and Au for various MoS 2 thicknesses, and that the screening lengths for each substrate are larger than 5 nm. By reporting the work function variation of MoS 2 on these substrates, this study aims to provide important insights into device design and contact engineering.

stacking nature, [5] strain, [6] and applied voltages. [7] Properties such as natural surface passivation, [8] high carrier mobility, [9] semiconducting band gaps, [1a] valley polarization, [10] strong light-mater interactions, [3,11] and the transitions from an indirect band gap in bulk form to a direct band gap in monolayer form [3,12] make them noteworthy materials to study. TMDCs such as molybdenum disulfide (MoS 2 ) have proven to be photoactive [13] and have been investigated as potential absorber layers in solar cells. [14] Many proof-of-concept devices have been constructed in the past few years, the majority of them based on exfoliated TMDC flakes. [13b,15] Exfoliation approaches are limited to the preparation of micrometer-scale devices and are challenging to scale to larger length scales. Even though there have been a few instances of larger scale TMDC solar cells. [16] In most of these cases, bulk MoS 2 or TMDC materials were used with layer thickness exceeding 100 nm. Therefore, these approaches could not benefit from the intrinsic properties of mono-and few-layer MoS 2 , such as an increased band gap [12] and high absorption coefficient in thin layers, [13b] and do not exploit the potential for transparent and semi-transparent photovoltaic applications. [17] In order to take advantage of the unique mono-and few layer properties of MoS 2 as absorption layers in solar cells, the TMDC films need to be integrated in a device stack that can separate and extract charge carriers from the TMDC light absorbing layer. Charge separation can be realized with carrierselective contact materials, such as titanium oxide (TiO x ) acting as an electron selective contact [18] and molybdenum oxide (MoO x ) acting as a hole selective contact. [19] Where these selective contacts help separate the generated charge carriers due to different work functions of the contact material. [20] TiO x and MoO x have already been reported to form type II heterostructures with MoS 2 allowing for charge separation. [21] One aim of this paper is to investigate the influence of the adjacent TiO x and MoO x contacts on the optoelectronic properties of monoand few layer exfoliated MoS 2 flakes, different from a similar study by Xu et al., [22] that also explores the relationship between MoS 2 and carrier selective contacts. The MoS 2 absorber layers, in our study are transferred onto the contact materials in order to avoid possible damage of the ultrathin absorber during contact deposition, instead of being sandwiched between silicon dioxide (SiO 2 ) and metal oxides. As 2D materials are sensitive Transition metal dichalcogenides are an exciting class of new absorber materials for photovoltaic applications due to their unique optoelectronic properties in the single to few-layer regime. In recent years, these materials have been intensively studied, often utilizing conventional substrates such as sapphire and silicon dioxide on silicon. This study investigates the optical properties of molybdenum disulfide (MoS 2 ) mono-, bi-, and mul...

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