Ruth Shinar, Iowa State University
Tunable Perovskite-Based Photodetectors in Optical Sensing
Written by Victor A. Rodriguez-Toro
Compact spectroscopic platforms for (bio)chemical sensing have been proposed in the past. Typically, it consists of a light source in the visible range that sends an optical pulse to photoexcite a phosphorescent dye, which is embedded in a thin film like polystyrene (PS). Once the visible light is turned off (end of the optical pulse), a signal of photoluminescence (at longer wavelength than the light source) is emitted from the dye and sensed by a photodetector (PD). Characteristics of the emitted signal (amplitude and decay time) depend on the interaction of the dye with the analyte (e.g., oxygen) to detect. As the analyte concentration increases, the amplitude of the photoluminescence signal is lower, and the decay time is shorter. Therefore, two measurement modes to determine the analyte concentration can be established by monitoring (1) the optical intensity or (2) decay time. The latter constrains the response time of the light source and the PD to be in the order of 1 ms. Furthermore, it is desirable that the PD to have a low external quantum efficiency (EQE) at the wavelengths of the light source, but a high EQE at the wavelengths of the emitted signal of photoluminescence.
Shinar and co-workers present the assessment of various photodetection technologies. First, inorganic PDs based on inorganic materials such as amorphous silicon are evaluated making evident their long response time (~250 ms) and the need for external filters. Second, organic photodetectors (OPDs) based on the polymer P3HT and the acceptor PCBM were evaluated showing low EQE in the region of interest for detection.
Finally, perovskite photodetectors (PPDs) were evaluated showing a high EQE, fast response times, and the ability to have systems with broadband and narrowband photodetection sensitivity.