Metal halide perovskites (MHPs) are direct bandgap semiconductors with excellent potential and perspectives to become an alternative to traditional semiconductors in the implementation of future devices for optoelectronics and photonics. Furthermore, MHPs have shown remarkable performance for potential optoelectronic applications beyond photovoltaics. The continuous development in smart devices and microsystems for the control of industrial processes, biomedical sensors and instruments, visible and NIR light communications (in the internet of things, for example), object imaging, and cameras for artificial intelligence and robotics is triggering new demands for photodetection concepts and their integration in photonic chips. However, for the explosion of such future photodetector technologies, some other requirements are important: low cost and low CO₂ footprint in fabrication, low operation voltage, small volume, high speed, flexibility, biocompatibility, solar-blind and many other features (for different applications). Therefore, a real and very interesting technology for a future generation of photodetectors can arise on the basis of MHPs, given their excellent optoelectronic properties and the fact that they can be synthesized at low temperatures via fast and simple processes, and films can be easily formed by low-cost solution processing techniques (spin-coating, spray-coating, dip-coating, doctor blading, inkjet printing). Among the MHPs, lead-free perovskite compounds are the most promising non-toxic alternative for developing photodetectors.

This study investigates the development of (PEA_0.5,BA_0.5)₂FA₉Sn₁₀I₃₁-based photodetectors fabricated using inkjet printing on both glass and flexible substrates, emphasizing their potential for advanced optoelectronic applications. The focus is on optimizing the crystallization process of (PEA_0.5,BA_0.5)₂FA₉Sn₁₀I₃₁ layers, ensuring high-quality films with minimal defects, and enhancing charge carrier mobility. The fabrication process employs solution-based techniques compatible with large-scale production, making the devices suitable for integration into wearable electronics and curved displays. Various strategies, such as interface engineering, compositional tuning, and passivation layers, were explored to improve stability and light sensitivity. The research demonstrates that inkjet-printed (PEA_0.5,BA_0.5)₂FA₉Sn₁₀I₃₁ layers (200 nm thickness) exhibit uniform crystal structures, enabling high responsivity and stable performance under different environmental conditions. The fabricated devices exhibited high responsivity across a wide range of light intensities and wavelengths, including visible and near-infrared regions. Persistent photoconductivity due to carrier trapping mechanisms was observed, highlighting the need for further engineering to enhance performance stability. Photoconductive properties were evaluated using continuous and modulated light sources. Devices on glass substrates showed higher efficiency and responsivity compared to flexible PET substrates, likely due to substrate interactions and defect levels. Responsivities ranged up to 50 A/W under low light intensity, with stability improvements observed even after 30 days of operation. Notably, the devices showed improved performance over time, indicating slow film curing and effective encapsulation. The results highlight the potential of inkjet-printed (PEA_0.5,BA_0.5)₂FA₉Sn₁₀I₃₁ photodetectors for next-generation photonic applications, where flexibility and low-cost fabrication are crucial. Despite the promising performance, challenges such as sensitivity to moisture and oxidation in tin-based perovskites remain, impacting long-term device stability. This research provides valuable insights into the practical deployment of lead-free perovskites in photodetection technologies.