Copper(I)‐Arsine Clusters with a Near‐Unity Phosphorescence Quantum Yield for X‐Ray Scintillation and LED Applications

Rare‐earth element‐free materials that exhibit strong room temperature phosphorescence (RTP) and X‐ray scintillation properties are gaining global interest incessantly in the recent years. This work reports a series of easily synthesizable cubane Cu 4 I 4 ‐triarsenic clusters [Cu 4 I 4 (R 3 As) 3 L] (L = none or nitrile), that exhibit a strong yellow‐green RTP with quantum efficiencies up to 100% and short decay times (4.4–4.9 µs). The title cluster complexes display X‐ray scintillation properties with a record ultralow detection limit (18.1 nGy s −1 ) and a perfectly linear dose rate response within a remarkably wide dose rate window (0–640 µGy air s −1 ). The cluster [Cu 4 I 4 (Ph 3 As) 3 ] is highlighted as an efficient phosphor for UV‐pumped white and yellow LED devices, demonstrating an excellent white spectrum with a CIE index of (0.32,0.33) and bright yellow emission, respectively. These results may stimulate the future efforts in designing highly efficient arsenic‐based RTP materials and enriching the Cu 4 I 4 cluster family.