Stretchable and colorless freestanding microwire arrays for transparent solar cells with flexibility

Transparent solar cells(TSCs)are emerging devices that combine the advantages of visible transparency and light-toelectricity conversion.Currently,existing TSCs are based predominantly on organics,dyes,and perovskites;however,the rigidity and color-tinted transparent nature of those devices strongly limit the utility of the resulting TSCs for realworld applications.Here,we demonstrate a flexible,color-neutral,and high-efficiency TSC based on a freestanding form of n-silicon microwires(SiMWs).Flat-tip SiMWs with controllable spacing are fabricated via deep-reactive ion etching and embedded in a freestanding transparent polymer matrix.The light transmittance can be tuned from ~10 to 55% by adjusting the spacing between the microwires.For TSCs,a heterojunction is formed with a p-type polymer in the top portion of the n-type flat-tip SiMWs.Ohmic contact with an indium-doped ZnO film occurs at the bottom,and the side surface has an Al2O3 passivation layer.Furthermore,slanted-tip SiMWs are developed by a novel solventassisted wet etching method to manipulate light absorption.Finite-difference time-domain simulation revealed that the reflected light from slanted-tip SiMWs helps light-matter interactions in adjacent microwires.The TSC based on the slanted-tip SiMWs demonstrates 8%efficiency at a visible transparency of 10% with flexibility.This efficiency is the highest among Si-based TSCs and comparable with that of state-of-the-art neutral-color TSCs based on organic–inorganic hybrid perovskite and organics.Moreover,unlike others,the stretchable and transparent platform in this study is promising for future TSCs.

Hybridization of different types of exceptional points

A large number of different types of second-order non-Hermitian degeneracies called exceptional points(EPs)were found in various physical systems depending on the mechanism of coupling between eigenstates.We show that these EPs can be hybridized to form higher-order EPs,which preserve the original properties of the initial EPs before hybridization.For a demonstration,we hybridize chiral and supermode second-order EPs,where the former and the latter are the results of intra-disk and inter-disk mode coupling in an optical system comprised of two Mie-scale microdisks and one Rayleigh-scale scatterer.The high sensitivity of the resulting third-order EP against external perturbations in our feasible system is emphasized.

Impact of non-Hermitian mode interaction on inter-cavity light transfer

Understanding inter-site mutual mode interaction in coupled physical systems is essential to comprehend large compound systems,as this local interaction determines the successive multiple inter-site energy transfer efficiencies.In the present study,we demonstrate that only the non-Hermitian coupling can correctly account for the light transfer between two coupled optical cavities.We also reveal that the non-Hermitian coupling effect becomes crucial as the system dimension decreases.Our results provide important insight for handling general-coupled devices in the subwavelength regime.