Organic X-Ray Image Sensors Using a Medium Bandgap Polymer Donor with Low Dark Current

The development of portable X-ray detectors is necessary for diagnosing fractures in unconscious patients in emergency situations.However,this is quite challenging because of the heavy weight of the scintillator and silicon photodetectors.The weight and thickness of X-ray detectors can be reduced by replacing the silicon layer with an organic photodetectors.This study presents a novel bithienopyrroledione-based polymer donor that exhibits excellent photodetection properties even in a thick photoactive layer(~700 nm),owing to the symmetric backbone and highly soluble molecular structure of bithienopyrroledione.The ability of bithienopyrroledione-based polymer donor to strongly suppress the dark current density(Jd~10−10 A cm^(−2))at a negative bias(−2.0 V)while maintaining high responsivity(R=0.29 A W−1)even at a thickness of 700 nm results in a maximum shot-noise-limited specific detectivity of D_(sh)^(*)=2.18×10^(13)Jones in the organic photodetectors.Printed organic photodetectors are developed by slot-die coating for use in X-ray detectors,which exhibit D_(sh)^(*)=2.73×10^(12)Jones with clear rising(0.26 s)and falling(0.29 s)response times upon X-ray irradiation.Detection reliability is also proven by linear response of the X-ray detector,and the X-ray detection limit is 3 mA.

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.