Highly Sensitive Dual‐Band Switchable between Ultraviolet and Visible Region Photomultiplication Type Polymer Photodetectors

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AbstractDual‐band photomultiplication type polymer photodetectors (PM‐PPDs) are achieved with the structure of ITO/PDIN/poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)benzidine] (poly‐TPD):2,2′‐((2Z,2′Z‐(12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2′′,3′′:4′,5′]thieno‐[2′,3′:4,5] pyrrolo‐[3,2‐g]thieno[2′,3′: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 (Y6) (100:2, wt/wt)/MoO3/poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) (100:2, wt/wt)/Al. Electron traps can be formed with Y6 surrounded by poly‐TPD or with PC71BM surrounded by P3HT. Trapped electrons near ITO/PDIN or Al electrode can assist hole tunneling injectionunder forward or reverse bias, respectively. The dual‐band PM‐PPDs exhibit ultraviolet spectral response under forward bias dependent on trapped electron distribution near ITO/PDIN electrode, while presenting visible spectral response under reverse bias determined by trapped electron distribution near Al electrode. The performance of dual‐band PM‐PPDs can be optimized by decreasing P3HT:PC71BM layer thickness. The optimal dual‐band PM‐PPDs exhibit external quantum efficiency (EQE) of 2800% at 350 nm under +10 V bias with full‐width at half‐maximum of 80 nm, while achieving EQE of 7500% at 430 nm under −10 V bias. The EQE values of optimal dual‐band PM‐PPDs are markedly improved by raising bias, reaching 13 000% at 350 nm under +16 V bias and 27 000% at 430 nm under −16 V bias. This work provides an effective method to prepare dual‐band PM‐PPDs by manipulating the interfacial trapped electron distribution.