Peer review of: A bilateral interfacial passivation strategy promoting efficiency and stability of perovskite quantum (2020)

Reviewers' comments: 

Reviewer #1 (Remarks to the Author): 

In this manuscript, the authors try to passivate the defect at the both of the top and bottom side 
perovskite surface, and suppress the non-radiative recombination. Based on this bilateral passivation 
strategy, QD films passivated by phosphine oxide organic molecule (POOMs) makes the devices 
achieve a maximum EQE of 18.7% and current efficiency of 75 cd/A, luminance reach 21000 cd/cm2. 
This could be the most efficient of QD perovskite light-emitting diodes. More importantly, due to the 
substantially binding, the passivation strategy makes the films and LEDs to be of greatly enhanced 
stability. The results shown in this manuscript are very encouraging for QD perovskite LEDs, although 
the efficiency is not as high as thin film perovskite LEDs. The paper could be considered for publication 
if the authors could address following questions: 
1)QD shows very high PLQY while it is in solution, why the PL will be quenched when forming as solid 
state? The authors claimed in page 3 lines 69-71: “As is known that a large part of fluorescence is lost 
when the colloidal QDs transform into the QD solids, this is because massive defects would be 
introduced inevitably during the film-forming process.”, The massive defects could be one reason, 
another reason could the aggregation of QDs as I think. The authors should give more explanations. 
2)P=O bond related molecular have been used for single side passivation of perovskite and enhancing 
the emission (Nature Photonics, 2018, 12, 355, Nature Communications, 2018, 9, 570). The 
passivation molecular adopted in this manuscript with the similar key structure. It could be very 
meaningful if the authors could give a deep mechanism of P=O passivation for perovskite materials. 
3)The processing details of the passivation molecular such as concentrations, temperature are missing 
in the experimental parts. And three molecular diphenylphosphine oxide-4-(triphenylsilyl)phenyl 
(TSPO1), triphenylphosphine oxide (TPPO) and bis(2-(diphenylphosphino)phenyl) ether oxide(DPEPO) , 
why the TSPO1 work the best? 
4)For the passivation layer deposited on the perovskite, what solvent is used for processing of the 
molecular such as TSPO1, does this solvent could destroy the perovskite layer? 



Reviewer #2 (Remarks to the Author): 

In this manuscript, Xu et al. report green-emitting perovskite quantum dot LEDs with bilateral 
interfacial passivation using phosphine oxide molecules (POOMs), and they achieve a high EQE of 
18.7%. This work is interesting, however, the mechanism is not clearly elucidated: 

1. It is well-known that P=O endgroup passivates perovskites, including reports such as ACS Energy 
Letters 2016, 1, 438; Nature Photonics 2018, 12, 355; Nature Communications 2018, 9, 570. The 
authors use TSPO1, DPEPO and TPPO for passivation, and claim that TSPO1 enables the highest PLQY, 
but without any rational explanation. What is the difference between various POOMs? 

2. It is confusing how POOM can form bonding with the perovskite in different solid layers. The FTIR 
signal change from 1188 to 1184 cm-1 is quite small and might be an experimental error. The authors 
should provide stronger evidence to confirm the interaction between POOM and the perovskite. 

3. It is confusing why R-P=O is compared with R-SH, R-COOH and R-NH3 in Figure 1e. How about R-
S=O, R-C=O and R-N=O? Can they also passivate QDs? 

4. The authors declare that bilateral interfacial passivation decreases the defect density and improves 
PLQY (Figure 2e). However, they only compare the initial films with unilateral (on the top of QD film) 

Editorial Note: Parts of this peer review file have been redacted as indicated to remove third-party material where no permission to publish could be obtained.and bilateral P=O passivation, but without unilateral (on the bottom of QD film). Please provide more 
comparison between POOM/QD, POOM/QD/POOM and QD/POOM, including but not limited to the PLQY, 
defect density, crystal structure (TEM), morphology (AFM) and EL performance. 

5. TSPO1 and DPEPO are both fluorescent hosts widely used in organic light-emitting diodes and show 
LUMO energy level of 2.5 eV and HOMO energy level of 6.8 eV. But Figure 4 indicates that they do not 
affect the energy level of QD films, which is confusing. 

6. The authors describe a 15-fold enhancement in the device operational lifetime from 0.8 to 13 hours 
in the abstract, but not mention the initial luminance. And, what is the lifetime at a higher initial 
luminance, for example, 1000 cd/m2? 

7. In addition, there are some details. 
(i) The bond order in Line 129, Page 6 is 2.0, different from the value in Figure 1e. 
(ii) The thickness of the QD film in LED should be provided. 
(iii) The TTPO should be TPPO in Figure 4h. 
(iv) In both the abstract and LED section, the authors show a very high luminance of 21,000 cd/cm2, 
which equals 2.1×108 cd/m2. But Figure 4c only depicts a luminance lower than 15,000 cd/m2, which 
is confusing. 



Reviewer #3 (Remarks to the Author): 

This manuscript proposed bilateral interfacial passivation by P=O group to achieve efficient and stable 
perovskite QLEDs. The novelty is bilateral interfacial passivation, while the P=O passivation method is 
not new. The EQE of QLEDs here for green LED is still lower than film-based perovskite LEDs, what 
impressive is the outstanding stability. The authors need to explain why bilateral interfacial 
passivation can achieve better stability. 

1, According to the authors, this work presents 'the most efficient and stable green perovskite QLEDs 
recorded in this field up to now'; however, considering the results from Lin K, et al, Nature 562, 245-
248 (2018) an EQE of >20% is conceivable for green PeLED. First, the authors need to point out the 
state-of-art perovskite LEDs on any types of perovskite, not just QLEDs. Second, it seems the EQE in 
this paper of QLEDs is not as high as film-based perovskite LEDs, the authors need to highlight what is 
the advantage of their green perovskite QLEDs compared to other film-based perovskite LEDs. 

2, What is the critical role the passivation plays for the enhancement of device stability should be 
further analyzed. Can the POOMs prevent the ion migration, or oxygen and water penetration for the 
prolonged lifetime? Is there any direct evidence for the difference between passivated and 
unpassivated devices when they reach their T50 lifetime, such as the QDs' structure or surface 
uncoordinated Pb ions? Related result can help to further understand the decay mechanism of the 
perovskite QDs and the passivation effect. 

3, P=O passivation method by n-trioctylphosphine oxide has been reported by Nature Photonics 12, 
355–361(2018). The authors should give enough credits to this reference. The main difference here is 
the bilateral P=O passivation strategy. The P=O passivation strategy is not something new. In order to 
explain the function of bifacial P=O passivation, the best experimental setup is a comparison of 
without passivation, passivation at PTAA/QD, passivation at QD/TPBi, and passivation at both 
PTAA/QD and QD/TPBi for Figure 4 and 5. This can explain whether passivation at both sides are 
important or just one side is enough. 

4, The devices have worked under a bias voltage of ~7 V, in this condition, whether the wavelength 
red-shift appears due to ion-migration or joule heat? 

5, The POOMs might promote the injection balance for both carriers (electron and hole injection), or 
supply a blocking barrier for excess carriers, resulting in the better electrical excitation efficiency. 
Comparison of the hole-only devices with the electron-only ones might supply a clear explanation in 
Figure 6. 

6, It contains many typos which should be corrected, such as line 21 in page 4, line 7-9 in page 11, 
and caption of Figure S1, etc. The caption of Figure 1a is not consistent with the image, didn’t found 
any red double-headed arrow in Figure 1a. 



Reviewer #4 (Remarks to the Author): 

This MS by Xu et al demonstrates a bifacial passivation approach to realize PQDs with very high PLQY 
and also demonstrates their use a efficient LEDs. The authors perform a lot of measurements and 
show enhancements in the optical and electronic properties and attribute this to passivation of traps. 
This is a reasonable study, but I am not sure why this is novel. I do not think this represents the 
technical innivation required for a MS in Nature comm for the following reasons. 
1/ Many groups have demonstrated PQDs pioneered by Kovalenko and co workers, that show near 
unity PLQY. Why is the starting point of these samples at 40-50% ? It is obvious that passivation will 
work. The important experiment is to try a PDQ with >90% PLQY and then see if this works? 
2/ There is a dearth of literature of using surface passivation molecules on low-dimensional hybrid 
perovskites. Why is this special ? 
3/ The stability of the LEDs was tested at 120 cd/m2. This is where the LED injection current is very 
low. If the authors claim stability, this should be tested at higher current densities. 

Based on these comments, I do not think this MS is suitable for Nature Comm.