A combination of novel techniques such as a solvent-free thin-film deposition, perovskite patterning, and B-10 back-fill technique enables the high neutron detection efficiency in a perovskite-based microstructured thermal neutron detector. High-efficiency cesium lead bromide (CsPbBr3) perovskite-based microstructured detectors are demonstrated here. Trenches up to 10 mu m deep are etched into the CsPbBr3 thin films using a novel dry etching process involving a combination of HBr and Ar plasma. The microstructured diodes are then backfilled with isotopically enriched boron as neutron conversion material via a sedimentation process to preserve the perovskite integrity. The fabricated microstructured CsPbBr3 thermal neutron detectors show an efficiency of 4.3%. This represents >1.2x efficiency improvement over planar silicon (3.5%) and >2x efficiency improvement over planar CsPbBr3 (2.1%) detectors, respectively. More importantly, gamma-ray discrimination of 10(7) is measured in CsPbBr3-based microstructured neutron detectors.