Significant prolongation in the green afterglow of SrAl
2O
4:Dy
3+ was achieved by adding 10 mol% H
3BO
3 into the starting material. The surface morphology, crystalline structure, chemical composition, photoluminescence, afterglow and decay characteristics of the phosphor were characterized by scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, transmission electron microscopy, photoluminescence and photoexcitation spectroscopy, respectively. It was found that the afterglow time constant of the green afterglow from SrAl
2O
4:Dy
3+ phosphor could be enhanced over 100 folds from 53 to 5538 s after the addition of 10 mol% H
3BO
3 flux. No traces of Eu were found in the phosphors within the 1 μg/g detection limit of the inductively coupled plasma atomic emission spectrometry. By employing meta generalized gradient approximation to describe the exchange–correlation functional, the band structures of SrAl
2O
4:Dy
3+ were calculated within the framework of density functional theory. The ground state of Dy
3+ ions and the defect leve
ls of
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lsi0002" class="mathmlsrc">6304719&_mathId=si0002.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=ba467c2959a274e0e291d756de0d8249">6304719-si0002.gif"> and
lsi0003" class="mathmlsrc">6304719&_mathId=si0003.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=34be0e3f1ce4f9c3ed0cefc1d96bb1ab">20" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022231316304719-si0003.gif"> were quantitatively determined in the band gap of SrAl
2O
4. A possible afterglow mechanism was proposed to shed fresh light on the green afterglow of SrAl
2O
4:Dy
3+. The significant prolongation in the afterglow of SrAl
2O
4:Dy
3+ can be attributed to the H
3BO
3 flux introduced
lsi0003" class="mathmlsrc">6304719&_mathId=si0003.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=34be0e3f1ce4f9c3ed0cefc1d96bb1ab">20" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022231316304719-si0003.gif"> in the host lattice.