Rapid Design of Homogeneous Direct-LED Irradiation Modules Using a Geometric Radiation Field Model

Abstract Photochemical process development critically relies on efficient and reproducible parameter screening, which consequently requires irradiation modules capable of delivering high photon fluxes with well-defined and homogeneous light fields. However, state-of-the-art indirect irradiation modules are inherently limited in the achievable photon flux by optical losses during reflection onto the reactor surface. This work aims for the rational design and optimization of a direct LED irradiation module that delivers high and spatially homogeneous irradiation for a multibatch screening photoreactor. To this end, a computationally efficient geometric radiation field model was developed to rapidly predict spatial irradiance distributions and enable large-scale parameter screening across LED number, placement, and height. The model was validated against radiometric measurements and ray tracing simulations, achieving relative deviations from the measurements below 11% in mean irradiance and below 2.5% in homogeneity for a simple reflector-free reference arrangement, while reducing computation time by 4 orders of magnitude compared to ray tracing. Combining the geometric model with Monte Carlo sampling and multiobjective Pareto optimization based on homogeneity and photon utilization enabled identification of near-optimal module height, LED number, and spatial arrangement. Experimental validation demonstrated that the optimized direct irradiation module increased the mean irradiance by a factor of up to 8.2 compared to the existing indirect irradiation concept while using only 2.67 times more LEDs, alongside an improvement in homogeneity from approximately 0.67 to more than 0.80. The addition of the tested diffuse PTFE reflectors further increased the mean irradiance by up to 38% and reduced the sensitivity to LED placement. The presented approach enables efficient, scalable irradiation module optimization and is expected to improve the throughput and reliability of photochemical parameter screening.