Growth Regulation of Pentacene-Doped p-Terphenyl Crystals on Their Physical Properties for Promising Maser Gain Medium

Abstract

Doped organic crystals possess wide application potential in the fields of scintillators and maser gain medium. However, the growth of doped organic single crystals with bulk size and high quality is still a big challenge due to the well-known poor crystallization capacity for organic materials. Here we report a thermal field-elevating technique to realize optimized growth conditions for organic crystals, where a pentacene-doped p-terphenyl single crystal with a size of Φ18 mm × 80 mm is obtained. Crystal quality and doping concentration effect on the optical properties of the crystalline wafers are investigated. The results show that p-terphenyl single crystal as an ordered matrix not only separates the guest molecules from one another to prevent quenching, but also constructs a Shpolskii-type host as an orienting medium to increase the interaction of pentacene with light. Moreover, a slightly reducing growth atmosphere is found to generate longer excitation lifetimes and a larger magnetic susceptibility of the grown doped crystal, which may be favorable for the spin-related physical process occurring in the excited state.

Pentacene in 1,3,5-Tri(1-naphtyl)benzene: A Novel Standard for Transient EPR Spectroscopy at Room Temperature

“…Below this limit, pentacene molecules randomly replace p-terphenyl molecules with the long axis of the pentacene parallel to the long axis of the displaced host molecule [20,21]. For crystal growth either co-sublimation [20,23] or the Bridgman method is widely used [1,12]. Both methods require specialist equipment which means that samples of p-terphenyl doped with pentacene cannot be prepared in many laboratories.…”

Long Persistent Luminescence of Melt‐Grown Bulk‐Sized Doped Organic Crystals

“…As shown in Figure a, different doping concentrations generated little influence on the outlook of the crystals under natural light, including color and crystallinity. This is quite different to the case of pentacene‐doped p ‐terphenyl, for which a doping concentration higher than 0.1% is hard to realized, [ 16 ] indicating that benzophenone analogs possess much higher compatibility with p ‐terphenyl. All the doped crystals show blue emissions under 365 nm UV illumination (Figure 4b).…”

“…The doped crystals were grown by thermal field‐elevating technique, a modified Bridgman method that we have recently adopted to grow pentacene‐doped p ‑terphenyl crystals. [ 16 ] First we employed benzophenone (BP) and its derivatives, 4‐bromobenzophenone (BBP) and 4,4′‐dibromobenzophenone (DBBP) as guest molecules, being doped into p ‐terphenyl host crystal, with the doping concentration of 2 wt%. Detailed growth procedures are presented in the Supporting Information.…”

“…In this report we utilized our recently developed thermal field‐elevating melt growth technique to grow a variety of host–guest crystals with LPL property. [ 16 ] Compared with the solution method, melt growth can obtain bulk‐sized crystals with a size in centimeter. More importantly, the doping concentration can be quantitatively tuned with uniform distribution in the entire crystal.…”

Invasive optical pumping for room-temperature masers, time-resolved EPR, triplet-DNP, and quantum engines exploiting strong coupling

“…Finally, considering (v), pumping that is too intense could easily damage the organic crystals [23]. Making large, optically flawless molecular crystals is also difficult, especially if the host is doped at high concentrations [24]. The crystals used in P:TP masers to date have typically had dimensions of 3-40 mm [11,12,19].…”