Room-temperature quantum sensing with photoexcited triplet electrons in organic crystals

Quantum sensors have notably advanced high-sensitivity magnetic field detection. Here, we report quantum sensors constructed from polarized spin-triplet electrons in photoexcited organic chromophores, specifically focusing on pentacene-doped para-terphenyl (≈0.1 essential quantum sensing properties at room temperature: electronic optical polarization and state-dependent fluorescence contrast, by leveraging differential pumping and relaxation rates between triplet and ground states. We measure high optically detected magnetic resonance (ODMR) contrast ≈16.8% of the triplet states at room temperature, along with long coherence times under spin echo and CPMG sequences, T_2=2.7μs and T_2^DD=18.4μs respectively, limited only by the triplet lifetimes. The material offers several advantages for quantum sensing, including the ability to grow large (cm-scale) crystals at low cost, the absence of paramagnetic impurities, and the diamagnetism of electronic states used for sensing when not optically illuminated. Utilizing pentacene as a representative of a broader class of spin triplet-polarizable organic molecules, this study highlights new potential for quantum sensing in chemical systems.