Large-scale roll-to-roll printed,flexible and stable organic bulk heterojunction photodetector

A flexible and stable photodetector shows great potential applications in intelligent wearable devices,health monitoring,and biological sensing.The high-output fabrication of flexible and stable photodetector via the large-scale printing process would accelerate its commercialization.Herein,a high performance,flexible organic bulk heterojunction(BHJ)photodetector with good stability is designed and fabricated via a large-scale roll-to-roll(R2R)micro-gravure printing technique on polyethylene terephthalate(PET)or paper substrate,in which the organic BHJ active layer is structured with[6,6]-phenyl C_(61)butyric acid methyl ester(PCBM)and a donor-acceptor copolymer,i.e.,employing 4,8-bis(2-ethylhexylthiophene)benzo[1,2-b;3,4-b′]dithiophene(BDTT)as the donor unit and 5,8-bis(5-thiophen-2-yl)-6,7-difluoro-2,3-bis(4-ethylhexyloxy-1-mata-luorophenyl)quinoxaline(ffQx)as the acceptor unit(PBDTT-ffQx).The PBDTT-ffQx/PCBM BHJ photodetector shows a broad photoresponse in ultraviolet and visible light,a high detectivity(D^(*))value up to 6.19×10^(11)Jones,and an excellent Iphoto/Idark as high as 5.6×10^(2).It exhibits excellent flexibility and stability.Its performance parameters could maintain over 80%of original values after bending 10,000 cycles or exposing in ambient condition(humidity~50%,temperature~30℃)for 50 days without any encapsulation.More importantly,the R2R micro-gravure printed PBDTT-ffQx/PCBM BHJ active layer is great homogeneous,and the responsivity(R)values of photodetector arrays show a very narrow distribution.The research results show that a high-performance PBDTT-ffQx/PCBM BHJ photodetector with well reliability and reproducibility can be fabricated via the R2R micro-gravure printing technique,which provides an available strategy for fabricating large-area and flexible electronic and optoelectronic devices.