Nanowire-embedded polymer photomultiplication photodiode with EQE over 250,000%

Abstract

In this work, a photomultiplication-type organic photodiode (PM-OPD) with a nanowire (NW)-embedded polymer morphology is introduced aiming prolonged carrier lifetime and enhanced carrier mobility, both of which contribute to more efficient gain generation mechanism. Growth of well-defined NWs with low structural defects within poly(3-hexylthiophene-2,5-diyl) (P3HT):[6], [6]-phenyl-C₇₁-butyricacid-methylester (PC₇₁BM) (100:1 w/w) bulk-heterojunction (BHJ) active layer is achieved using a typical aging method, confirmed by UV–Vis absorption spectroscopy, atomic force microscopy and grazing incidence X-ray diffraction analyses. Transient photocurrent analyses clearly show that the NW-embedded P3HT morphology efficiently suppresses electron detrapping from localized PC₇₁BM, leading to prolonged minority carrier recombination time. Space charge limited current study shows that gradual increase in NW density in BHJ film can lead to increase of hole mobility along the vertical direction, presumably due to increased formation of efficient percolation pathways. Thanks to such synergetic contributions of NW-embedding, remarkable increase of external quantum efficiency (EQE) up to 250,000%, responsivity up to 1300 A W⁻¹ and high specific detectivity up to 6.3 × 10¹³ Jones can be realized by embedding an optimal amount of NW into conventional PM-OPD structured as ITO/PEDOT:PSS/BHJ/Al. This work shows the importance of nanomorphology of the active layer in PM-OPD to achieve high EQE.