Correction to: Nature https://doi.org/10.1038/s41586-018-0835-2, published online 16 January 2019.

In Fig. 1c of this Letter, the orange axis label of the graph should have read ‘FDPP upconversion photoluminescence (AU)’ instead of ‘TTBP upconversion photoluminescence (AU)’. The original Letter has been corrected online.