Suppressing the Dark Current Under Forward Bias for Dual-Mode Organic Photodiodes

Tremendous research efforts are developed to suppress the reverse dark current ( J d ) and enhance the responsivity of organic photodiodes (OPDs). The functional layers of traditional OPDs usually follow the principle of energy level alignment to make unobstructed photo-carriers transport under reverse bias, but this inevitably leads to a large forward J d . Herein, a universal strategy is proposed to manipulate the carrier dynamics and effectively suppress the forward J d of OPDs, that is, tuning the energy level and electron traps of the anode interface layers (AILs). The bandgap and electron traps of typical organometallic chelate AIL (PEIE-Co) can be well controlled by adjusting the component ratio of PEIE and metal ions. The wide bandgap increases the carrier injection barrier under reverse and forward bias, endowing OPD with a much lower J d ; the electron traps induce hole tunneling injection by capturing photo-generated electrons under forward bias, thereby enabling the photomultiplication effect. The obtained OPD exhibits photoconductive/photomultiplication working mode at reverse/forward bias and the specific detectivity approaches ≈10 13 /10 12 Jones, showing promise for adaptively detecting faint and strong light. This study presents an intelligent strategy to achieve dual-mode OPDs, paving the way for the multifunctional development of photodetectors.