posted on 2024-01-03, 13:35authored byUdara
M. Kuruppu, Mohammad A. Rahman, Mahesh K. Gangishetty
Lead-free low-dimensional copper-based metal halides
are promising
luminescent materials for broadband LEDs owing to their broad self-trapped
exciton (STE) emission. However, recently, in 1D CsCu2I3, a discrepancy between their electroluminescence (EL) and
photoluminescence (PL) has been observed. As a result, the overall
output color from LEDs is significantly different than the anticipated
emission. To unveil the origin of this discrepancy, here, we provide
comprehensive analyses and show that the shift in the EL is caused
neither by any structural/optical interactions between CsCu2I3 and electron transport layers (ETL) nor by the degradation
of 1D CsCu2I3. Instead, it depends on the carrier
imbalance on CsCu2I3, mainly due to the difference
in the electron mobility of the ETLs and the electron density on the
CsCu2I3 layer. By varying the ETLs, different
colored 1D CsCu2I3 LEDs with peaks at 556, 590,
and 647 nm are fabricated, and a maximum luminance of over 2000 cd/m2 is achieved for a 556 nm LED. Further, by limiting the electron
mobility and injection to 1D CsCu2I3 using an
insulating LiF layer at the CsCu2I3/ETL interface,
more red-shifted LEDs are achieved confirming the critical role of
electron density on the EL characteristics of 1D CsCu2I3.