Triplet‐Triplet Annihilation Enhances Photochemical Curing Contrast for Vat‐Based 3D Printing

ABSTRACT Vat photopolymerization is a leading additive manufacturing strategy, yet its fidelity across length scales is fundamentally constrained by the sublinear dependence of curing rate on excitation intensity, which promotes overcure and loss of resolution. Here, we present a systematic, mechanism‐based comparison of Type I, Type II, and triple‐triplet annihilation photopolymerization (TTAP) within digital light processing (DLP) 3D printing. Using resins with matched optical densities, we show that TTAP uniquely exhibits a superlinear initiation response that suppresses overcure, yielding superior z ‐confinement and balanced x , y ‐fidelity compared to Type I and II photoinitiation. Under ambient conditions and low‐intensity green light (525 nm, 100 mW cm −2 ), TTAP resins achieve rapid curing (≈45 mm/h) while reliably fabricating features spanning tens of micrometers to millimeters, including complex geometries with overhangs, unsupported structures, and enclosed cavities. By enabling contrast‐enhanced curing at LED‐accessible intensities, this work establishes TTAP as a distinct and versatile photoinitiation paradigm and provides a framework for improving resolution and fidelity in visible‐light vat photopolymerization among other emerging additive manufacturing platforms.