Organic perovskites are promising semiconductor materials for advanced photoelectric applications. Their fluorescence typically shows a negative temperature coefficient due to bandgap change and structural instability. In this study, a novel perovskite-based composite with positive sensitivity to temperature was designed and obtained based on its inverse temperature crystallization, demonstrating good flexibility and solution processability. The supercritical drying method was used to address the limitations of annealing drying in preparing high-performance perovskite. Optimizing the precursor composition proved to be an effective approach for achieving high fluorescence and structural integrity in the perovskite material. This perovskite-based composite exhibited a positive temperature sensitivity of 28.563% °C for intensity change and excellent temperature cycling reversibility in the range of 25–40 °C in an ambient environment. This made it suitable for use as a smart window with rapid response. Furthermore, the perovskite composite was found to offer temperature-sensing photoluminescence and flexible processability due to its components of perovskite-based compounds and polyethylene oxide. The organic precursor solvent could be a promising candidate for use as ink to print or write on various substrates for optoelectronic devices responding to temperature.