Managing the interference effects from multiple thin-layer structures allows for the control of optical transmittance and reflectance properties -often with very high precision. Widely used and technologically significant examples of such structures are antireflection coatings (ARCs) and distributed Bragg reflectors (DBRs), which rely on the careful control of destructive and constructive interference, respectively, between incident and reflected/transmitted radiation. While these structures have been known for over a century and have been extremely well investigated for many decades, the growing emergence of printable, large area electronics based on soluble materials brings a new emphasis. Namely the availability and use of materials in multilayer environments that are capable of transferring well-established ideas to a solution-based production.Here, we demonstrate the solution-fabrication of ARCs and all dielectric mirrors based on a DBR design utilizing alternating layers of recently developed organic/inorganic hybrid materials comprised of poly(vinyl alcohol) (PVAl), cross-linked with titanium oxide hydrates, and commercially available bulk commodity plastics. Our dip-coated ARCs exhibit an 88 % reduction in reflectance across the visible compared to uncoated glass, and fully solution-coated DBRs provide a reflection of >99 % across a 100 nm spectral band in the visible region. Detailed comparisons with transfer-matrix methods (TMM) highlight the excellent optical quality of the structures. The investigation also demonstrates the extremely low optical losses and impressive interface qualities the constituent layers exhibit. Furthermore, when exposed to elevated temperatures, the hybrid material can display a notable, reproducible and irreversible change in both the refractive index and film-thickness while maintaining excellent optical performance. In addition to allowing a degree of post-deposition tuning of the photonic structures, this may lend itself to thermo-responsive applications, including security features and product-storage environment monitoring.
The ever increasing library of materials systems developed for organic solar‐cells, including highly promising non‐fullerene acceptors and new, high‐efficiency donor polymers, demands the development of methodologies that i) allow fast screening of a large number of donor:acceptor combinations prior to device fabrication and ii) permit rapid elucidation of how processing affects the final morphology/microstructure of the device active layers. Efficient, fast screening will ensure that important materials combinations are not missed; it will accelerate the technological development of this alternative solar‐cell platform toward larger‐area production; and it will permit understanding of the structural changes that may occur in the active layer over time. Using the relatively high‐efficiency poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′′′‐di(2‐octyldodecyl)‐2,2′;5′,2′′;5′′,2′′′‐quaterthiophen‐5,5′′′‐diyl)] (PCE11):phenyl‐C61‐butyric acid‐methyl‐ester acceptor (PCBM) blend systems, it is demonstrated that by means of straight‐forward thermal analysis, vapor‐phase‐infiltration imaging, and transient‐absorption spectroscopy, various blend compositions and processing methodologies can be rapidly screened, information on promising combinations can be obtained, reliability issues with respect to reproducibility of thin‐film formation can be identified, and insights into how processing aids, such as nucleating agents, affect structure formation, can be gained.
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