Up-conversion lasing actions are normally difficult to realize in light-emitting materials due to small multi-photon absorp-tion cross section and fast dephasing of excited states during multi-photon excitation. This paper reports an easily ac-cessible up-conversion amplified spontaneous emission (ASE) in organic-inorganic hybrid perovskites (MAPbBr3) films by optically exciting broad gap states with sub-bandgap laser excitation. The broad absorption was optimized by adjust-ing the grain sizes in the MAPbBr3 films. At low sub-bandgap pumping intensities, directly exciting the gap states leads to 2-photon, 3-photon, and 4-photon up-conversion spontaneous emission, revealing a large optical cross section of multi-photon excitation occurring in such hybrid perovskite films. At moderate pumping intensity (1.19 mJ/cm2) of 700 nm laser excitation, a significant spectral narrowing phenomenon was observed with the full width at half maximum (FWHM) de-creasing from 18 nm to 4 nm at the peak wavelength of 550 nm, simultaneously with a nonlinear increase on spectral peak intensity, showing an up-conversion ASE realized at low threshold pumping fluence. More interestingly, the up-con-version ASE demonstrated a giant magnetic field effect, leading to a magneto-ASE reaching 120％. In contrast, the up-conversion photoluminescence (PL) showed a negligible magnetic field effect (< 1％). This observation provides an evid-ence to indicate that the light-emitting states responsible for up-conversion ASE are essentially formed as spatially exten-ded states. The angular dependent spectrum results further verify the existence of spatially extended states which are polarized to develop coherent in-phase interaction. Clearly, using broad gap states with spatially extended light-emitting states presents a new approach to develop up-conversion ASE in organic-inorganic hybrid perovskites.

Tangyao Shen;Jiajun Qin;Yujie Bai;Jia Zhang;Lei Shi;Xiaoyuan Hou;Jian Zi;Bin Hu

Department of Physics,Fudan University,Shanghai 200433,China;Department of Physics,Chemistry and Biology(IFM),Link?ping University,Link?ping 58183,Sweden;Department of Materials Science and Engineering,University of Tennessee,Knoxville,Tennessee 37996,USA

光电进展（英文版）

[1]Tangyao Shen;Jiajun Qin;Yujie Bai;Jia Zhang;Lei Shi;Xiaoyuan Hou;Jian Zi;Bin Hu-.Giant magneto field effect in up-conversion amplified spontaneous emission via spatially extended states in organic-inorganic hybrid perovskites)[J].光电进展（英文版）,2022(02):33-41

cessible,evid

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