Research on the Performances of the DPP-based Narrow Bandgap Polymer Constructed Photovoltaic Photodetectors
Organic/polymer photodetectors have attracted great attention due to their outstanding advantages,inclu-ding controllable spectral,adjustable bandgap,simple processing technology,flexibility,and large area fabrication.Herein,three oligothiophene moieties 3,3'-dimethoxy-substituted bithiophene(OT),3,4-dimethoxy-thiophene(O),and 3,6-dimethoxythieno[3,2-b]thiophene(OTT)were selected respectively as electron-rich units,and pyrrole[3,4-c]pyrrole-1,4-dione(DPP)was used as electron-deficient unit to prepare three D-A type narrow bandgap conjuga-ted polymers(CPs)POT-DPP,PO-DPP,and POTT-DPP.The systematic study was conducted on the thermal sta-bility,optical absorption,aggregation,energy levels of polymers as well as the photovoltaic performance,charge transfer,recombination,and specific detectivity(D*)of their photovoltaic photodetectors.It was found that the pho-todetectors based on POTT-DPP which bearing the larger conjugated planes paired with PC71BM achieved the best photodetection performance with the highest D*of 1.87×1011 Jones at 400 nm and 1.67×1011 Jones at 850 nm,re-spectively.These results mainly contributed by the higher and balanced hole/electron mobility,well suppressed bi-molecular recombination,trap assisted recombination and desired surficial morphology of photoactive layer.This work demonstrated that enlarging the conjugated area of the electron rich units of D-A conjugated polymers can ef-fectively adjust the bandgap,promote the carrier migration,and suppress the recombination processes in their photo-detectors,thereby promoting the photo detectivity of the corresponding devices.
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