Nature magazine reported an organic photomultiplication photodiode with an external quantum efficiency EQE close to 2000%.
Original Article Link: PM-OPD EQE 2000%
“Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors“
From smart lighting in the lobby of a building to the cruise control of a cars, photodetectors (PDs) play an important role in our daily life. Generally, applications that require fast detection of weak signals use inorganic avalanche photodetectors. As the automotive industry moves toward self-driving cars, it requires lower cost, higher sensitivity, and more form-free photodetectors with wavelength selectivity. The photodetectors PD made of organic semiconductors can provide these characteristics.
The article reported a completely vacuum-treated PM-OPD based on a low acceptor content (3 wt%) ZnPc:C60 material system, achieving a maximum external quantum efficiency EQE of nearly 2000% at -10 V. In addition, it was found that the optimal operating conditions maximize external quantum efficiency EQE while maintaining low dark current, resulting in D* of 2.2 × 10 12 Jones at 670 nm. From measured external quantum EQE spectra show that direct excitation of the CT state will also lead to photomultiplications, which is confirmed by internal quantum efficiency IQE higher than 100% in the entire absorption region. Under −5 V reverse bias, the external quantum efficiency EQE of the PM-OPD surpasses that of an optimized pin-photodiode, demonstrating the potential for application in microcavity CT-OPDs.
Figure 1. The device structure of PhotoMultiplier type PhotoDetector PM-OP which has the external quantum efficiency over 100% EQE.
Figure 2. The external quantum efficiency EQE of PM-OPD. Under the condition of -10V voltage bias, the external quantum efficiency EQE of PM-OPD can be as high as 2000%, showing the photomultiplication effect of this device structure.
Figure 3. The external quantum efficiency EQE comparison of PM-OPD and traditional PIN photodiode. The red dotted line shows the EQE spectrum of a traditional ZnPc:C60 (50 wt%) pin photodiode, and the black solid line shows PM-OPD, both at 0 V. The solid line shows PM-OPD (3 wt% C60) under bias, as shown in the legend. At -5 V, the higher injection provided by energy level bending results in higher external quantum efficiency EQE than traditional pin photodiodes.