Vacuum-free lamination via controlled polymer adhesion for selective photogeneration and photodetection

This study attempts to develop a reproducible thin-film formation technique called vacuum-free(VF)lamination,which transfers thin films using elastomeric polymer-based laminating mediators.Precisely,by controlling the interface characteristics of the mediator based on the work of adhesion,VF lamination is successfully performed for various thicknesses(from 20 to 240 nm)of a conjugated photoactive material composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-bʹ]dithiophene))-alt-(5,5-(1ʹ,3ʹ-di-2-thienyl-5ʹ,7ʹ-bis(2-ethylhexyl)benzo[1ʹ,2ʹ-c:4ʹ,5ʹ-cʹ]dithiophene-4,8-dione)](a polymer donor)and 2,2ʹ-((2Z,2ʹZ)-((12,13-bis(2-butyloctyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2ʹʹ,3ʹʹ:4ʹ,5ʹ]thieno[2ʹ,3ʹ:4,5]pyrrolo[3,2-g]thieno[2ʹ,3ʹ:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile(a nonfullerene acceptor).Interestingly,the organic photovoltaic and photodetecting applications,prepared by the VF lamination process,showed superior performance compared to those of devices prepared by conventional spin-coating.This is due to the overturned surface morphology,which led to enhanced charge transport ability and blocking of the externally injected charge.Thus,the reproducible VF lamination process,exploiting an adhesion-based elastomeric polymer mediator,is a promising thin-film formation technique for developing efficient next-generation organic optoelectronic materials consistent with the solution process.

Reconfigurable transmissive metasurface with a combination of scissor and rotation actuators for independently controlling beam scanning and polarization conversion

Polarization conversion and beam scanning metasurfaces are commonly used to reduce polarization mismatch and direct electromagnetic waves in a specific direction to improve the strength of a wireless signal.However,identifying suitable active and mechanically reconfigurable metasurfaces for polarization conversion and beam scanning is a considerable challenge,and the reported metasurfaces have narrow scanning ranges,are expensive,and cannot be independently controlled.In this paper,we propose a reconfigurable transmissive metasurface combined with a scissor and rotation actuator for independently controlling beam scanning and polarization conversion functions.The metasurface is constructed with rotatable unit cells(UCs)that can switch the polarization state between right-handed(RHCP)and left-handed circular polarization(LHCP)by flipping the UCs to reverse their phase variation.Moreover,independent beam scanning is achieved using the scissor actuator to linearly change the distance between the UCs.Numerical and experimental results confirm that the proposed metasurface can perform beam scanning in the range of 28°for both the positive and negative regions of a radiation pattern(RHCP and LHCP beams)at an operational frequency of 10.5 GHz.

Ultra-flexible semitransparent organic photovoltaics

Ultra-flexible organic photovoltaics(OPVs)are promising candidates for next-generation power sources owing to their low weight,transparency,and flexibility.However,obtaining ultra-flexibility under extreme repetitive mechanical stress while maintaining optical transparency remains challenging because of the intrinsic brittleness of transparent electrodes.Here,we introduce straindurable ultra-flexible semitransparent OPVs with a thickness below 2μm.The conformal surface coverage of nanoscale thin metal electrodes(<10 nm)is achieved,resulting in extremely low flexural rigidity and high strain durability.In-depth optical and electrical analyses on ultrathin metal electrodes showed that the devices maintain over 73%of their initial efficiency after 1000 cycles of repetitive compression and release at 66%compressive strain,and the average visible light transmittances remain higher than 30%.To our knowledge,this is the first systematical study on mechanical behaviors of strain-durable ultra-flexible ST-OPVs through precise adjustment of each ultrathin electrode thickness toward the emergence of next-generation flexible power sources.