Peer review of: Charge and exciton dynamics of OLEDs under high voltage nanosecond pulse: towards injection la  (2020)


RR2
 Reviewers' Comments:
 Reviewer #1:
 Remarks to the Author:
 This paper presents a thorough analysis of the various electronic and optical processes occurring in
 PLEDs, and demonstrates a successful path for predicting the quantitative role of each of these
 processes. It should definitely be published, but I am not sure that Nat. Comm. is the proper
 venue, as I still have serious concerns about any strong impact it might have. Specifically, my
 concerns are as follows:
 1. Despite the authors’ rebuttal, one of the simple bottom lines resulting from the myriad reports
 published over 30 years on PLEDs vs small molecule OLEDs is that the former are inherently
 inferior to the latter. And the danger of excitons getting too close to the metal cathode in the
 former is just one reason. Admittedly, in the revised manuscript the authors included results on
 small molecule BSBCz OLEDs, but these were limited to simulations of BSBCz OLEDs reported in
 the literature.
 2. In the Abstract the authors write “The challenge in analysing these processes concurrently has
 been the major hurdle in realizing injection lasing.” That’s not true. The major hurdle in realizing
 injection lasing is the quenching of excitons by other excitons and by polarons, which are
 processes that become massive at high current densities, b/c they are bimolecular. Hence this
 statement is not true and, worse still, misleading.
 3. Also in the Abstract the authors write “The experimental data is simulated accurately and
 results highlight crucial differences between optical and electrical pumping and provide a robust
 test platform for any organic material.” The crucial differences between optical and electrical
 pumping are so obvious they hardly need any highlighting.
 4. Finally, still in the Abstract, the authors write that “The key findings provide essential protocols
 for material and device design for injection lasing.” After so many efforts for so many years, it is
 abundantly clear that if we ever witness an organic injection laser, it will not be b/c we have the
 “essential protocols for materials and device design” but b/c the groundbreaking group that will
 demonstrate it will have thought outside the box, in a way we do not currently imagine. Indeed,
 one of the justifications for the efforts invested in, e.g., OLETs was the opportunity to largely
 separate charge carriers from the recombination zone and thus minimize exciton quenching by
 polarons. And we know how well that worked.
 5. While the modeling itself appears to be reasonably comprehensive, there is no mention of losses
 to surface plasmons, which are significant in devices where the emission zone is close to the metal
 cathode. This is particularly relevant to PLEDs, where the layer directly following the emissive layer
 is the ultrathin buffer (7 nm Ba in this paper) followed by the metal (typically Al) cathode. All the
 more reason why the focus on PLEDs in comparing the modeling and simulations to experimental
 results is less than convincing.
 Reviewer #2:
 Remarks to the Author:
 The authors have addressed my concerns completely and made corresponding revisions and added
 additional supporting data, which can be accepted without further revision.
 Reviewer #3:
 Remarks to the Author:

 The revised manuscript is well written and organized. Thus I believe that the revised article should
 be accepted for publication as it is.