Using charge collection narrowing to tune from broadband to narrowband all-polymer photodetectors

Abstract We report an all-polymer photodiode comprising a new electron-transporting polymer, PNNTH , that contains naphthalene diimide and thiazole moieties. PNNTH has strong absorption at around 670 nm and an electron mobility of ≈10 −4 cm 2 V −1 s −1 . Bulk heterojunction films composed of PNNTH blended with the donor polymer, PBDTT-FTTE , in a weight ratio of 1:2 were found to have electron and hole mobilities of ≈10 −5 cm 2 V −1 s −1 and ≈10 −4 cm 2 V −1 s −1 , respectively. The photoresponse of conventional and inverted organic photodiodes containing the blend could be tuned from broadband (400–800 nm) to narrowband (50 nm full-width-at-half-maximum) simply by changing the thickness of the all-polymer blend. The narrowband response was achieved using the charge collection narrowing mechanism, which was enhanced by the unbalanced charge mobility. Transfer matrix-based optical modelling confirmed the wavelength dependence of the photoresponse. For both the broadband and narrowband photodiodes, the specific detectivity was greater than 10 11 Jones.