Correction to “Efficient Interfacial Upconversion Enabling Bright Emission at an Extremely Low Driving Voltage in Organic Light-Emitting Diodes”

Abstract

S. Izawa, M. Morimoto, S. Naka, et al.: Efficient Interfacial Upconversion Enabling Bright Emission at an Extremely Low Driving Voltage in Organic Light-Emitting Diodes. Adv. Optical Mater. 10, 2101710 (2022). https://doi.org/10.1002/adom.202101710.

In the above article, the authors would like to correct an error identified in the calculation of the external quantum efficiency (EQE). Specifically, the error originates from the choice of wavelength interval (nm) used in the numerical integration of spectral data. In the original manuscript, the wavelength interval was taken to be 1.4 nm, corresponding to the stated instrumental spectral resolution of the spectrometer. However, the actual wavelength interval of the acquired spectral data was 0.57–0.60 nm. After re-evaluating the calculation using this data interval as the wavelength interval, we found that the corrected values are approximately three-sevenths of those reported previously. The corrected calculation procedure was quantitatively validated by comparison with independently calibrated measurements obtained using an EQE measurement system based on an integrating sphere.

The authors are therefore replacing the original Figures 3 and S6 with the new Figures 3 and S6 below, which are based on the verified procedure.

FIGURE 3 | EQE as a function of injected current density for (a) rubrene/C₆₀ (black circle), rubrene/C₈-PTCDI (red triangle), DBP-doped rubrene/C₆₀ (blue cross), and DBP-doped rubrene/C₈-PTCDI (purple square) devices with an emitter layer thickness of 50 nm; and (b) DBP-doped rubrene/C₈-PTCDI devices with different emitter layer thicknesses, i.e., 20 nm (gray diamond), 50 nm (purple square), 100 nm (blue triangle), 150 nm (orange cross), and 200 nm (green circle).

The corrected Figure S6 is listed in the latest version of the Supporting Information.

It is important to note that this correction only applies to the absolute values. All relative comparisons between materials and experimental conditions remain unchanged, as they are scaled uniformly. The corrected maximum efficiency of our upconversion (UC)-organic light-emitting diode (OLED) is 1.20%, which is two orders of magnitude higher than that in the previous UC-OLED (0.043%). This correction does not affect the main claim of the original paper, two orders of magnitude higher EQE and bright UC emission at a low voltage.

In addition, the authors would like to correct Φ_PL: absolute photoluminescence quantum efficiency (PLQE) values of pristine rubrene and rubrene doped with 0.5 vol% DBP films in Table S1. The reevaluated PLQE of the pristine rubrene film is 2.8% (29.1% in the original paper), and that of the rubrene doped with 0.5 vol% DBP film is 44.9% (72.6% in the original paper). In the previous experiment, the rubrene films were encapsulated, and the epoxy resin, applied to the edge of the substrate, swelled the rubrene, making it emissive. The swelled edge part was excited in an integrating sphere for PLQE measurement and contributed to additional emission. The corrected data were measured on the film without encapsulation. The authors are therefore replacing the original Table S1 with the new Table S1 in the latest version of the Supporting Information.

To compare the PL intensity of different doping concentrations of DBP, the authors are adding normalized PL spectra of pristine and DBP-doped rubrene films at 500 nm as Figure S2b in the latest version of the Supporting Information, in addition to the original Figure S2 of PL spectra normalized at the maximum peak intensity. The peak intensity reaches its maximum at the 0.5% doping concentration primarily used in the OLED devices in this paper.

Based on the corrected EQE_Max and Φ_PL, the authors recalculated Φ_Loss and are therefore replacing the original Table 2 with the new Table 2 below.

Additionally, the authors would like to correct an error in the unit of luminance. The labeled “cd/cm²” in Figure 2b,d, and Figures S3, S5, and S7 in the Supporting Information were incorrect. These should be corrected to “cd/m²”.

FIGURE 2 | (a) J–V and (b) L–V curves for rubrene/BCP control (gray diamond), rubrene/C₆₀ (black circle), rubrene/C₈-PTCDI (red triangle), DBP-doped rubrene/C₈-PTCDI (green cross) without a rubrene interlayer, and DBP-doped rubrene/C₈-PTCDI (purple square) devices. (c) EL emission spectra of rubrene/C₈-PTCDI (red) and DBP-doped rubrene/C₈-PTCDI (purple) devices under a constant applied current (123 mA/cm²). (d) J–V and corrected L–V curves of rubrene/C₈-PTCDI (red triangle) and DBP-doped rubrene/C₈-PTCDI (purple square) devices measured using a photodetector. The EL intensity was corrected to correspond with that measured using the luminance meter in b. (e) Photograph of a DBP-doped rubrene/C₈-PTCDI device operated by a 1.5-V battery.

The corrected Figures S3, S5, and S7 are listed in the latest version of the Supporting Information.

The authors apologize for any confusion this may have caused and state that the scientific conclusions of the original article are unaffected.