Image Capture Against Strong Backlight Using Molecular-Switch-Embedded Organic Photodiode
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The photocurrent of organic photodiodes (OPDs) exhibits early saturation under increased incident light intensities. Consequently, OPDs cannot easily detect objects against strong backlight, for example, sunlight. We address this problem by introducing a light-intensity-dependent transition of the operation mode. In particular, when the incident light intensity passes a threshold intensity, the operation mode of the OPD autonomously changes to overcome early photocurrent saturation. The photoactive layer is doped with a strategically designed and synthesized molecular switch (1,2-bis-(2-methyl-5-(4-cyanobiphenyl)-3-thienyl)tetrafluorobenzene; DAB). The suggested OPD exhibits a typical performance with an external quantum efficiency (EQE) ＜ 100% under low-intensity light illumination and a photomultiplication behavior with an EQE ＞ 100% under high-intensity light illumination, resulting in the extension of the photoresponse linearity to a light intensity of 434 mW cm−2.