Noise Reduction Based on Experimental Investigation of Barrier Energy and Structural Innovation with Multijunction Photoactive Layer for Efficient Organic Photodetector

Organic photodetectors (OPDs) have emerged as promising alternatives to traditional inorganic photodetectors due to their high absorption coefficients and tunable optoelectronic properties. OPDs with bulk-heterojunction (BHJ) structures have suffered from high dark current and increased noise due to charge injection at the interfaces, which lowers the signal-to-noise ratio and sensitivity in low-intensity illumination.
Herein, a theoretical analysis of the barrier-dependent charge injection mechanisms elucidates the influence of barrier energy on dark current in OPDs. To investigate the effect of acceptors in BHJ structures on dark current, OPDs are fabricated according to the types of acceptors in photosensitive layers, because anodic charge injection to acceptors has a major role in dark current under an applied reverse bias. [1] The origin of the dark current generated in an organic photodetector is observed through the modeling between current and voltage and current and barrier energy. Based on the modeling, the non-fullerene acceptor-based OPDs with high barrier energy show a high detectivity owing to suppressed charge injection.
Furthermore, this study explores strategies to focus on dark current suppression and photocurrent improvement of OPDs by innovating the active layer structure. [2] The introduction of a multiple-active layer structure A/BHJ, combining a BHJ with a single acceptor layer, enables improved charge separation while minimizing charge injection. A novel transfer-printing method is employed, ensuring the precise interface formation in the A/BHJ structure without solvent interference, leading to enhanced photocurrent and lower noise. These advancements position A/BHJ-based OPDs as viable solutions for high-sensitivity light detection and light-based wireless communication systems.
By investigating the mechanism related to barrier energy and developing the multijunction photoactive layer through the vacuum-free transfer process in organic photodetector, this work can help devise effective strategies based on materials and processes to suppress dark current for efficient organic photodetector operation.
[1] Jang et al., Adv. Funct. Mater., 2023, 33, 2209615
[2] Jang et al., Adv. Mater., 2024, DOI: 10.1002/adma.202406316