Optical Modeling-Assisted Characterization of Polymer:Fullerene Photodiodes

Abstract

In this paper, the practical viability of an organic bulk heterojunction (BHJ)-based photodiode is studied, including the analysis of dark current density ( $J_{d}$ in $hbox{A/cm}^{2}$), external quantum efficiency (EQE in percent), responsivity (R in A/W), noise-equivalent power (in $hbox{W/Hz}^{1/2}$), and specific detectivity (Jones in $hbox{cmHz}^{1/2}/hbox{W}$). The dark current was minimized down to 90 $hbox{pA/cm}^{2}$ in ${rm P}3{rm HT}:{rm PC}_{60}hbox{BM}$ BHJ photodiodes by increasing the thickness, whereas the EQE maintained high values. The measured noise current was $2.20times 10^{-13}$, $1.13times 10^{-13}$, and $1.94times 10^{-14} hbox{A/Hz}^{1/2}$ for 45-, 55-, and 65-nm BHJ photodiodes, respectively. With those values, the calculated detectivity obtained, given light of a 550 nm wavelength, was $2.55times 10^{11}$, $5.93times 10^{11}$, and $4.16times 10^{12}$ Jones, respectively. The results demonstrated a performance of polymer:fullerence photodiode near equivalent to that of Si-based photodiodes.