Feature issue introduction: persistent and photostimulable phosphors – an established research field with clear challenges ahead

Abstract

Persistent phosphors have the ability to emit light long after the excitation has ended, typically by using thermal energy to liberate previously trapped charges. Alternatively, also photons can be used for the detrapping, leading to optically stimulated luminescence (OSL). This particular field of phosphor research has seen a strong expansion over the past two decades, with a steady growth of the materials library, an improved structural and luminescence characterization and the development of novel applications. Despite this success, clear challenges lie ahead in terms of a deeper understanding of the trapping mechanism and an associated optimization of the energy storage capacity being crucial for many applications. This focus issue "Persistent and Photostimulable Phosphors" within Optical Materials Express features papers presented at the third International Workshop on Persistent and Photostimulable Phosphors (IWPPP 2015) held at the University of Texas at Arlington. 19326-19332 (2015

A Review of Mechanoluminescence in Inorganic Solids: Compounds, Mechanisms, Models and Applications

“…Piezoelectricity can originate from intrinsic properties of non-centrosymmetric compounds (excluding compounds with 432 point group) or centrosymmetric compounds that have proper types of lattice defects or microstructure [27,28,262]. A decrease of effective energy barriers of traps leads to the release of an extra amount of carriers with the help of mechanical load [189].…”

“…Carriers are often stored in traps created by dopants/co-dopants or by cation/anion vacancies in phosphors. They can also escape from these traps by thermal energy, resulting in the delayed emission of light, which is termed persistent luminescence and is now reasonably well understood (see Refs [25,26] for a review), although the nature of (de)trapping process at defects remains unclear [27]. Alternatively, charge carriers can also be released upon mechanical load and subsequently recombine with luminescent centres, eventually yielding ML.…”

Upconverted persistent luminescence in β-NaGd0.8Yb0.17Er0.03F4 and Zn1.33Ga1.335Sn0.33Cr0.005O4 associated nanoparticles

“…Persistent luminescence is an optical phenomenon in which luminescence is still ongoing for a long time after the end of excitation, lasting from minutes to hours. 1 Since the seminal work on SrAl2O4:Eu 2+ ,Dy 3+ by Matsuzawa et al 2 , the field has rapidly grown 3,4 , with reports of dozens of persistent materials by many groups around the world, [5][6][7][8][9][10][11][12][13] and growing applications, from toys, luminous watches and safety signs to in vivo and in vitro imaging, theranostics and therapy. 7,[14][15][16][17][18] The two luminescence mechanisms of UC and persistent luminescence are different.…”

Dynamics of Charges in Superlong Blacklight-Emitting CaB2O4:Ce3+ Persistent Phosphor

“…Since the first report on the application of near-infrared (NIR)-emitting persistent luminescent (PersL) phosphors, the interest in the development of new PersL materials has grown rapidly, particularly for real-time optical imaging. − PersL is an optical phenomenon in which the material continues to emit radiation for a significant time after the initial excitation has been seized, with a possibility of tuning the emission wavelength between the UV and NIR regions, depending upon the host–dopant combinations. − For hosts containing Ce 3+ as a dopant, the PersL can be tuned in the 385–625 nm range as a result of splitting and lowering of the Ce 3+ 5d 1 band due to interaction with the host crystal field . To exhibit efficient PersL, the mobility of the electron or its delocalization in the conduction band is an important condition.…”