Suppressed Trap Density Leads to Versatile p-i-n Heterojunction Photodiode with Enhanced Photovoltaic/Photodetection Dual-Function

Abstract

Multifunctional integration of optoelectronic devices within a single photodiode is in high demand for next-generation on-chip multifunctional integration and Internet of Things applications. Owing to the rapidity of nucleation-crystallization that is associated with the solution method, large trap state densities (Nt), and consequently, severe dark current densities, as well as recombination losses are generally induced, which are detrimental to the detectivity (D*) of organic photodetectors (OPDs) and to the open-circuit voltage (VOC) of organic photovoltaics (OPVs). Herein, a versatile p-i-n heterojunction organic photodiode with optimized vertical phase distribution and rational solid-state packing is fabricated via a layer-by-layer (LBL) deposition procedure entailing the introduction of a rylene-fullerene hybrid as a morphological modulator. This precisely controlled photodiode displayed suppressed Nt (2.5 × 1016 cm−3), low-lying Urbach energy Eu (23.2 meV), as well as synergistically reduced series resistance, dark current, and sub-bandgap radiative/non-radiative recombination losses. Consequently, this ternary-pseudo-bilayer-type photodiode exhibits excellent dual-function performance with an outstanding D* of 9.48 × 1011 Jones in self-powered OPD mode and a surprisingly suppressed energy loss of 0.538 eV in OPV mode. This study provides important insights into the mechanism and effects of trap density and energy disorder suppression in solution-processed multifunctional integrated photoelectric conversion diodes.