Optical detection of magnetic field is appealing for integrated photonics; however, the light-matter interaction is usually weak at low field. Here we observe that the photoluminescence (PL) decreases by > 40% at 10 mT in rubrene microcrystals (RMCs) prepared by a capillary-bridge assembly method. The giant magneto-PL (MPL) relies on the singlet-triplet conversion involving triplet-triplet pairs, through the processes of singlet fission (SF) and triplet fusion (TF) during radiative decay. Importantly, the size of RMCs is critical for maximizing MPL as it influences on the photophysical processes of spin state conversion. The SF/TF process is quantified by measuring the prompt/delayed PL with time-resolved spectroscopies, which shows that the geminate SF/TF associated with triplet-triplet pairs are responsible for the giant MPL. Furthermore, the RMC-based magnetometer is constructed on an optical chip, which takes advantages of remarkable low-field sensitivity over a broad range of frequencies, representing a prototype of emerging opto-spintronic molecular devices.

磁场的光学检测对集成光子学很有吸引力。然而，光与物质的相互作用在低场下通常很弱。在这里，我们观察到，通过毛细管桥组装方法制备的红荧烯微晶 (RMC) 中，光致发光 (PL) 在 10 mT 时降低了 > 40%。巨磁致发光（MPL）依赖于涉及三重态-三重态对的单重态-三重态转换，通过辐射衰变期间的单重态裂变（SF）和三重态聚变（TF）过程。重要的是，RMC 的尺寸对于最大化 MPL 至关重要，因为它影响自旋态转换的光物理过程。通过使用时间分辨光谱测量瞬发/延迟 PL 来量化 SF/TF 过程，这表明与三重态-三重态对相关的成对 SF/TF 是造成巨大 MPL 的原因。此外，基于RMC的磁力计构建在光学芯片上，它在广泛的频率范围内利用了卓越的低场灵敏度，代表了新兴光自旋电子分子器件的原型。