Controlling electron transfer in a lateral near-infrared polymer photodetector by adding higher-LUMO-level acceptors: a pathway to reduce dark current

Abstract

The narrow bandgap of a near-infrared (NIR) polymer and the large electrode spacing of a lateral structure are the main factors causing the high dark current of the NIR lateral polymer photodetector (L-PPD). In this work, a large potential barrier is formed by innovatively introducing higher-LUMO-level acceptors (TPBi) into the bulk heterojunction layer (PDPP3T:PC₆₁BM), which ensures that the electrons recombine with holes instead of exhibiting transmission. Based on this phenomenon, a new strategy is proposed to decrease the dark current. Simultaneously, the large built-in electric field induced by polystyrene (PS) doping is utilized to compensate for the photocurrent loss caused by TPBi doping. Compared with a PDPP3T : PS : PC₆₁BM L-PPD (1 : 1 : 3), a TPBi : PDPP3T : PS : PC₆₁BM (1 : 2 : 2 : 6) device exhibited significant performance improvements. The dark current (1.3 × 10⁻¹¹ A@V = −20 V) decreased by approximately 3 orders of magnitude, the I_ph/I_dark value (∼ 1.7 × 10⁴@405 nm, ∼ 1.4 × 10³@850 nm) increased by a factor of 1000-fold, and the response speed (5.3/1.8 ms) improved by nearly fivefold.