Figure 4
From: Photocarrier drift distance in organic solar cells and photodetectors
Normalized External Quantum Efficiencies (EQEs) shown as a function of themeasured photocurrent for the different active layer thicknesses of (a)PTB7:PC70BM blends and (b) PCDTBT:PC70BM blends.
The photocurrent is normalized to the space charge limited current(ISCLC), which is calculated from the measured chargetransport parameters using Equation 1. Whenthe actual measured photocurrent approaches the space charge limitedcurrent, substantial recombination losses manifest implying that theelectrode defined space charge density controls the critical drift distance(LD ∼ d, where d is the devicethickness). (c) Numerically simulated EQEs as a function of the photocurrentconfirm that the deviation is caused by the ISCLC, wherethe appearance of the first recombination losses can occur at a slightlylower photocurrent compared to ISCLC.
