Laboratory;
of;
Luminescence;
and;
Optical;
Information,;
Ministry;
of;
Education;
Institute;
of;
Optoelectronic;
Technology,;
Beijing;
Jiaotong;
University,;
Beijing;
100044,;
China;
of;
Material;
Science;
and;
Engineering,;
Beijing;
Institute;
of;
Technology,;
Beijing;
100081,;
China;