The Role of Energy Loss in Achieving Ultralow Dark Current Density in Organic Photodetectors

Abstract In this study, organic photodetectors (OPDs) are fabricated using the polymer donor D18 and four Y6 derivatives (Y6, L8‐BO, BTP‐eC9, and Y18), each exhibiting distinct surface energies and HOMO/LUMO energy levels. This allows the investigation of the impact of morphological variations and energy level alignment within the blend films on energy loss ( E _loss ), a key factor influencing near‐infrared (NIR) OPD performance. Grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) analysis reveals that the D18/Y18 blend film exhibits an optimized unique 3D‐packing, which significantly reduces trap density and minimizes non‐radiative recombination. As a result, OPDs based on D18/Y18 demonstrate the lowest E _loss , primarily due to their higher charge transfer energy ( E _CT ) and suppressed non‐radiative recombination. This effectively inhibits thermal carrier generation in which D18/Y18‐based OPDs, demonstrate an ultralow dark current density ( J _d ) of 3.95 × 10 ⁻¹⁰ A cm ⁻² , a high responsivity (R) of 0.48 A W ⁻¹ , and an exceptionally high detectivity ( D _shot *) of 4.24 × 10 ¹³ Jones at a bias of −2 V. D18/Y18‐based OPDs demonstrate superior performance in key metrics such as linear dynamic range, cutoff frequency, and response time, making them highly competitive in the field of OPDs.