Trans-Reflective Structural Color Filters Assisting Multifunctional-Integrated Semitransparent Photovoltaic Window

Biomimetic Colored Coating toward Robust Display under Hostile Conditions

Structural colors particularly of the angle-independent category stemming from wavelength-dependent light scattering have aroused increasing interest due to their considerable applications spanning displays and sensors to detection. Nevertheless, these colors would be heavily altered and even disappear during practical applications, which is related with the variation of refractive index mismatch by liquid wetting/infiltrating. Inspired by bird feathers, we propose a simple deposition toward the coating with angle-independent structural color and superamphiphobicity. The coating is composed of ∼200 nm-sized channel-type structures between hollow silica and air nanostructures, exhibiting a robust sapphire blue color independent of intense liquid intrusion, which duplicates the characteristics of the back feather of Eastern Bluebird. A high color saturation and superamphiphobicity of the biomimetic coating are optimized by manipulating the coating parameters or adding black substances. Excellent durability under harsh conditions endows the coating with long-term service life in various extreme environments.

Boosting the Performances of Semitransparent Organic Photovoltaics via Synergetic Near-Infrared Light Management

Semitransparent organic photovoltaics (ST-OPVs) offer promising prospects for application in building-integrated photovoltaic systems and greenhouses, but further improvement of their performance faces a delicate trade-off between the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT). Herein, the authors take advantage of coupling plasmonics with the optical design of ST-OPVs to enhance near-infrared absorption and hence simultaneously improve efficiency and visible transparency to the maximum extent. By integrating core-bishell PdCu@Au@SiO2 nanotripods that act as optically isotropic Lambertian sources with near-infrared-customized localized surface plasmon resonance in an optimal ternary PM6:BTP-eC9:L8-BO-based ST-OPV, it is shown that their interplay with a multilayer optical coupling layer, consisting of ZnS(130 nm)/Na3AlF6(60 nm)/WO3(100 nm)/LaF3(50 nm) identified from high-throughput optical screening, leads to a record-high PCE of 16.14% (certified as 15.90%) along with an excellent AVT of 33.02%. The strong enhancement of the light utilization efficiency by ≈50% as compared to the counterpart device without optical engineering provides an encouraging and universal pathway for promoting breakthroughs in ST-OPVs from meticulous optical design.

Semitransparent Organic Solar Cells with Homogeneous Transmission and Colorful Reflection Enabled by an ITO-Free Microcavity Architecture

Semitransparent organic photovoltaics (ST-OPVs), owing to the merits of high power generation, thermal insulation, and aesthetic features, have become a promising candidate for intellectual building- integrated photovoltaic windows. However, the traditional optical evaluation only focuses on the transmission properties and ignores the reflection behaviors. And the lack of quantitative descriptions for array appearance hinders implementation of ST-OPV based large-area modules. To tackle with these issues, an indium tin oxide (ITO)-free optical microcavity architecture into ST-OPVs for achieving high homogeneity in transmittance with controllable reflective appearances through tunning the thickness of individual component layers is introduced. A set of parameters based on optical characteristics of sub-units to provide a quantitative description for the transmittance brightness, transmissive and reflective color purity, and versatility of optical arrays, is further proposed. The optical simulations reveal that reflection modulation from blue to red colors can be realized for devices based on various bulk-heterojunction material systems through regulating the thickness of active layers and antireflection coatings. This work offers a viable design strategy for ST-OPVs toward applications in next-generation smart photovoltaic windows.

On the role of asymmetric molecular geometry in high-performance organic solar cells

Although asymmetric molecular design has been widely demonstrated effective for organic photovoltaics (OPVs), the correlation between asymmetric molecular geometry and their optoelectronic properties is still unclear. To access this issue, we have designed and synthesized several symmetric-asymmetric non-fullerene acceptors (NFAs) pairs with identical physical and optoelectronic properties. Interestingly, we found that the asymmetric NFAs universally exhibited increased open-circuit voltage compared to their symmetric counterparts, due to the reduced non-radiative charge recombination. From our molecular-dynamic simulations, the asymmetric NFA naturally exhibits more diverse molecular interaction patterns at the donor (D):acceptor (A) interface as compared to the symmetric ones, as well as higher D:A interfacial charge-transfer state energy. Moreover, it is observed that the asymmetric structure can effectively suppress triplet state formation. These advantages enable a best efficiency of 18.80%, which is one of the champion results among binary OPVs. Therefore, this work unambiguously demonstrates the unique advantage of asymmetric molecular geometry, unveils the underlying mechanism, and highlights the manipulation of D:A interface as an important consideration for future molecular design.

Dual-color emissive OLED with orthogonal polarization modes

Linearly polarized organic light-emitting diodes have become appealing functional expansions of polarization optics and optoelectronic applications. However, the current linearly polarized diodes exhibit low polarization performance, cost-prohibitive process, and monochromatic modulation limit. Herein, we develop a switchable dual-color orthogonal linear polarization mode in organic light-emitting diode, based on a dielectric/metal nanograting-waveguide hybrid-microcavity using cost-efficient laser interference lithography and vacuum thermal evaporation. This acquired diode presents a transverse-electric/transverse-magnetic polarization extinction ratio of 15.8 dB with a divergence angle of ±30°, an external quantum efficiency of 2.25%, and orthogonal polarized colors from green to sky-blue. This rasterization of dielectric/metal-cathode further satisfies momentum matching between waveguide and air mode, diffracting both the targeted sky-blue transverse-electric mode and the off-confined green transverse-magnetic mode. Therefore, a polarization-encrypted colorful optical image is proposed, representing a significant step toward the low-cost high-performance linearly polarized light-emitting diodes and electrically-inspired polarization encryption for color images.

Solution Processed Semi-Transparent Organic Solar Cells Over 50% Visible Transmittance Enabled by Silver Nanowire Electrode with Sandwich Structure

Photovoltaic windows with easy installation for the power supply of household appliances have long been a desire of energy researchers. However, due to the lack of top electrodes that offer both high transparency and low sheet resistance, the development of high-transparency photovoltaic windows for indoor lighting scenarios has lagged significantly behind photovoltaic windows where privacy issues are involved. Addressing this issue, this work develops a solution-processable transparent top electrode using sandwich structure silver nanowires, realizing high transparency in semi-transparent organic solar cells. The wettability and conducting properties of the electrode are improved by a modified hole-transport layer named HP. The semi-transparent solar cell exhibits good see-through properties at a high average visible transmittance of 50.8%, with power conversion efficiency of 7.34%, and light utilization efficiency of 3.73%, which is the highest without optical modulations. Moreover, flexible devices based on the above-mentioned architecture also show excellent mechanical tolerance compared with Ag electrode counterparts, which retains 94.5% of their original efficiency after 1500 bending cycles. This work provides a valuable approach for fabricating solution-processed high transparency organic solar cells, which is essential in future applications in building integrated photovoltaics.