Circular‐Polarization‐Sensitive Organic Photodetectors with a Chiral Nanopatterned Electrode Inverse‐Designed by Genetic Algorithm

Advanced Functional Materials www.afm-journal.de RESEARCH ARTICLE Circular-Polarization-Sensitive Organic Photodetectors with a Chiral Nanopatterned Electrode Inverse-Designed by Genetic Algorithm Kyung Ryoul Park1,2 Jewoong Lee3 In-Suk Choi3,4 Changsoon Kim2,5 1Program in Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Republic of Korea 2Inter-University Semiconductor Research Center, Seoul National University, Seoul, Republic of Korea 3Department of Materials Science and Engineering, Seoul National University, Seoul, Republic of Korea 4Research Institute of Advanced Materials, Seoul National University, Seoul, Republic of Korea 5Department of Intelligence and Information, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Republic of Korea Correspondence: In-Suk Choi (insukchoi@snu.ac.kr) Changsoon Kim (changsoon@snu.ac.kr) Received: 26 August 2025 Revised: 26 February 2026 Accepted: 3 March 2026 Keywords: chiral plasmonic nanocavity | circularly polarized light | genetic algorithm | inverse design | organic photodetector ABSTRACT A metal–dielectric–metal nanocavity with a chiral nanopatterned metal electrode provides an effective platform for circularly polarized photodetectors, which allows the chiral optical response and photon-to-charge conversion to be optimized with minimal mutual interference. We employ a genetic algorithm to inversely design the electrode pattern to maximize the chiral response while incorporating a vacuum-deposited small-molecule multilayer, which enables precise alignment of the photoactive layer with the helicity-dependent field distribution. The optimization yields a non-intuitive metal nanopattern that achieves a high dissymmetry factor (𝑔EQE = 1.32) of external quantum efficiency (𝜂EQE = 16.7%) at a target wavelength, outperforming a representative conventional chiral nanopattern. The fabricated device with the optimized electrode achieves 𝑔EQE = 0.67 and 𝜂EQE = 8.1% near the target wavelength, and simulations of the fabricated device geometry, accounting for curvature in the multilayer stack, confirm helicity-dependent plasmonic field distributions consistent with those of the idealized flat-layer device used in the optimization. These results demonstrate the effectiveness of our inverse design strategy and provide a framework for the development of high-performance thin-film chiral optoelectronic devices. 1 Introduction Chiral photodetectors are a class of optoelectronic devices that generate differential photocurrents depending on the helicity of incident circularly polarized light (CPL), enabling applications in quantum information processing [1, 2], spintronics [3, 4], magnetic data storage [5], and circular dichroism spectroscopy [6]. The performance of these devices is typically character- ized by two figures of merit: the external quantum efficiency (𝜂EQE), representing photon-to-charge conversion efficiency, and its dissymmetry factor, quantifying the circular dichroic response: 𝑔EQE = 2 ( 𝜂r EQE −𝜂l EQE ) 𝜂r EQE +