High-efficiency diamond fluorescence detection for magnetic sensing systems using a filter-free narrowband photodetector.

The magnetic sensitivity of sensors based on diamond nitrogen-vacancy (NV) center solid-state spin systems depends on the detection of diamond fluorescence emission. The commonly used broadband photodetectors (e.g., 300-1000 nm) require filters to suppress 532 nm excitation light and background noise, which both attenuates fluorescence signal intensity and complicates system integration. To address these limitations, we designed an organic narrow-band photodetector employing a non-fullerene binary active layer (SBDTIC:DIBSQ), achieving targeted detection of diamond spin fluorescence wavelengths. The optimized device demonstrates a spectral absorption peak at 679 nm with a full width at half maximum (FWHM) of 130 nm. Integration of this detector into a diamond NV center magnetic sensing system yielded a magnetic sensitivity of 22.6 nT·Hz^-1/2. These results validate replacing conventional broadband photodetector-filter combinations with our specialized device. This substitution offers dual advantages: enhanced performance and simplified integration for NV-based magnetometry.