Enhancing Infrared Photodetectors with 2D Supramolecular Organic Frameworks

Integrating 2D materials with bulk semiconductors is an important method to imrove optoelectronic performance. In composite devices, bulk semiconductors generally serve as the main body for photoelectric conversion and charge carrier separation, while 2D materials assist with charge transport and modulation. Traditional 2D materials like graphene and transition metal dichalcogenides face challenges during growth (exfoliation) and transfer processes, such as substrate dependence, fragility during transfer, and poor interface contact. The development of new organic 2D materials and composite strategies offers a promising solution to these problems.

Zeyun Xiao, Haofei Shi, and Xingzhan Wei, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Xin Zhao, Shanghai Institute of Organic Chemistry, China, have applied supramolecular organic frameworks (SOFs) to infrared photodetectors. This detector combines the 2D SOF material with lead salts, using the self-assembled SOF to enhance the inorganic semiconductor.

The SOF is easily prepared in aqueous solution at room temperature. As shown above, the process of making the SOF/inorganic semiconductor composite first, a triamine molecule with special side chains self-assembles with cucurbit[8]uril (CB[8]) in water to form the structured SOF. This SOF has a layered structure with tiny pores arranged in a honeycomb pattern. The SOF’s thickness is about 5.1 to 5.2 nm. Next, the SOF solution is applied to the surface of a lead-based (PbSe) semiconductor using spin-coating, which evenly spreads the SOF over the surface. The device is heated briefly to secure the SOF layer, and gold electrodes are added to allow the device to conduct electricity. The final step involves bonding the electrodes and sealing the device in nitrogen gas to protect it.

During the integration process, the ethylene glycol chain in the SOF forms coordination bonds with lead in the lead salt, where the lead salt generates charge carriers and the SOF backbone acts as the carrier transport pathway.

This composite device shows excellent infrared detection under a 500K blackbody and 1550 nm infrared illumination, achieving a detectivity of 6.3×10⁹ Jones under the 500K blackbody. Due to the SOF barrier hindering photogenerated and thermally excited holes, the device demonstrates low-noise characteristics. The composite device also shows high stability due to the SOF’s role in passivating defects and blocking unwanted charge. According to the researchers, this study highlights the multifunctional applicability of 2D SOF materials in optoelectronics, paving the way for innovative development of composite devices through a self-assembled organic-inorganic approach.