Retraction to Constructing interfacial potential barrier via a gradient configuration: an effective method to enhance energy-filtering effect

‘Constructing interfacial potential barrier via a gradient configuration: an effective method to enhance energy-filtering effect’ (National Science Review, published online: 3 September 2020, doi: 10.1093/nsr/nwaa223). The authors have alerted us that recent experimental work conducted indicates that some expiations of this manuscript need to be further discussed. In agreement with the authors, editors and publisher, National Science Review has therefore decided to retract the paper. The journal would like to apologise for any inconvenience caused to the reader.