We present the utilization of inorganic, organic, and hybrid (perovskite) thin film photodetectors in (bio)chemical sensing where OLEDs are used as the excitation source in compact devices. The sensitivity and feasible operational mode, whether monitoring the effect of the analyte concentration on the photoluminescence intensity or decay time following an OLED pulse will be discussed. While monitoring the PL decay time is the preferred operational mode, charge trapping and other defects impede the photodetectors’ response time, limiting the analysis dynamic range. Analytes tested include oxygen, glucose, lactate, and ethanol. Examples of all organic sensors for these analytes will be presented. The use of thin film photodetectors in on-chip (integrated all-organic) spectrometers will also be shown.