Light emission from vertically-grown quasi one-dimensional (1D) graphene nanostripes (GNSPs): Temperature and thickness independent ultra-long carrier lifetimes*

We have previously shown that our PECVD-grown, quasi-1D GNSPs exhibited perfect purity, high mobility [1] and strong broadband absorption [2]. Here we report broadband photoluminescence (PL) and ultra-long carrier lifetimes in GNSPs from time-resolved PL (TRPL) studies. GNSPs were deposited on quartz substrates to form uniform films with thicknesses of 5, 10, 20, 40 and 50 μm for the TRPL measurements. We used Nd:YAG laser at 355 nm with 10 ps pulse width and 0.1 mJ pulse energy under a repetition rate of 10Hz to carry out TRPL studies at temperatures from 15 K to 290 K. Detailed analysis of the TRPL data revealed two carrier lifetimes of τ1 (~ 1 ns) and τ2 (~ 10 ns), both were independent of either temperature or thickness, and the values were ~ 10³ times longer than any lifetimes reported to date for graphene-based materials. We attribute the ultra-long lifetimes to the nanoscale quasi-1D nature of GNSPs, which breaks the global inversion symmetry so that photo-excited hot electrons and holes are rapidly separated due to their large differences in mobility, a.k.a. the photo Dember effect.

[1] C.-C. Hsu et al., Carbon 129, 527 (2018).
[2] N.-C. Yeh et al., Nanotechnology 30, 162001 (2019).