All-Optical Electrochemiluminescence at Metal-Insulator-Semiconductor Diodes

Pt/InGa/n-Si/SiO/Pt devices were prepared by using standard chemical and sputtering processes. These systems are diodes comprising a frontside photoactive metal-insulator-semiconductor (MIS) n-Si/SiO/Pt junction and a backside Pt/InGa/n-Si Ohmic contact. Pt/InGa/n-Si/SiO/Pt was first characterized by dark-solid-state electrical and impedance measurements. Then, each side of the device was investigated by electrochemical means in the dark and under near-IR illumination at 850 nm in the luminol-H₂O₂ electrochemiluminescence (ECL) electrolyte. The results suggested the possibility of triggering an all-optical ECL (AO-ECL) at Pt/InGa/n-Si/SiO/Pt. This was confirmed by studying AO-ECL at the monolithic, all-integrated Pt/InGa/n-Si/SiO/Pt device, immersed in the ECL electrolyte. The conversion process can occur with good stability and the intensity of the visible emission (440 nm) depends on tunable parameters such as the illumination power density, O₂ concentration, or the concentration of added H₂O₂. These results are important for the next developments of AO-ECL in sensing and microscopy.