Fluorescence microscopy is a powerful imaging technique that enables the visualization of cellular structures and their function as well as observing dynamic processes such as neuronal activity with high sensitivity and spatial resolution. Performing fluorescence imaging in vivo is ideally based on implantable technology that enables precise light delivery and detection. For this, organic semiconductors may serve as suitable active elements for light emission and detection since they can be miniaturized to cellular scale and made mechanically flexible. Here, we present narrow-band organic light-emitting diodes used for fluorescence excitation in combination with organic photodiodes that detect light emitted by fluorophores and cells. We specifically focus on high sensitivity and spectral separation of light emission and detection. Our results present the first step towards integrated implants for fluorescence imaging in vivo.