Significant prolongation in the green afterglow of SrAl2O4:Dy3+ was achieved by adding 10 mol% H3BO3 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 SrAl2O4:Dy3+ phosphor could be enhanced over 100 folds from 53 to 5538 s after the addition of 10 mol% H3BO3 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 SrAl2O4:Dy3+ were calculated within the framework of density functional theory. The ground state of Dy3+ ions and the defect levels of an id="mmlsi0001" class="mathmlsrc"><a title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022231316304719&_mathId=si0001.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=aa5b8895e7a48c6ed20325b40a3a90d5">ass="imgLazyJSB inlineImage" height="14" width="21" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022231316304719-si0001.gif">a>an class="mathContainer hidden">an class="mathCode">ath altimg="si0001.gif" overflow="scroll">VO••ath>an>an>an>, an id="mmlsi0002" class="mathmlsrc"><a title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022231316304719&_mathId=si0002.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=ba467c2959a274e0e291d756de0d8249">ass="imgLazyJSB inlineImage" height="17" width="19" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022231316304719-si0002.gif">a>an class="mathContainer hidden">an class="mathCode">ath altimg="si0002.gif" overflow="scroll">VSr″ath>an>an>an> and an id="mmlsi0003" class="mathmlsrc"><a title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022231316304719&_mathId=si0003.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=34be0e3f1ce4f9c3ed0cefc1d96bb1ab">ass="imgLazyJSB inlineImage" height="17" width="20" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022231316304719-si0003.gif">a>an class="mathContainer hidden">an class="mathCode">ath altimg="si0003.gif" overflow="scroll">VAl″′ath>an>an>an> were quantitatively determined in the band gap of SrAl2O4. A possible afterglow mechanism was proposed to shed fresh light on the green afterglow of SrAl2O4:Dy3+. The significant prolongation in the afterglow of SrAl2O4:Dy3+ can be attributed to the H3BO3 flux introduced an id="mmlsi0003" class="mathmlsrc"><a title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022231316304719&_mathId=si0003.gif&_user=111111111&_pii=S0022231316304719&_rdoc=1&_issn=00222313&md5=34be0e3f1ce4f9c3ed0cefc1d96bb1ab">ass="imgLazyJSB inlineImage" height="17" width="20" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022231316304719-si0003.gif">a>an class="mathContainer hidden">an class="mathCode">ath altimg="si0003.gif" overflow="scroll">VAl″′ath>an>an>an> in the host lattice.