A LEAP TOWARDS ENVIRONMENTALLY FRIENDLY, EFFICIENT, AND STABLE PEROVSKITE PHOTODETECTORS

Abstract

Metal halide perovskite (ABX3) is a material with the potential to revolutionize the photodetector industry because of its low cost, easy fabrication, and excellent optoelectronic properties. However, its toxicity, environmental stability and scalability limit its application. This thesis takes a leap towards environmentally friendly, efficient, stable, and scalable perovskite photodetectors. A scalable technique, solution-shearing, is used to create methylammonium lead iodide (MAPbI3) perovskite photodetectors and chemical additives are used as treatments to improve their performance and stability simultaneously. The figures of merit for photodetectors are evaluated, and the photodetectors show a record specific detectivity (D*) for perovskite photodetectors (1.53 x 1017 Jones). The devices demonstrate the viability of MAPbI3 in large scale photodetector applications. In addition, two-dimensional (2D) perovskites have immense potential to further improve the stability of perovskite photodetectors because of their long hydrophobic molecule (L). In the next research project, novel 2D perovskites (L2An-1BnX3n+1) are created and the largest crystal size for a 2D perovskite film is achieved. The champion perovskite photodetector using the 2-thiophenemethylamonnium (ThMA) L molecule shows a record responsivity (R) of ~ 4.6 x 105 A W-1 for perovskite photodetectors owing to its large crystal size and another record D* of over 1018 Jones. The two reports demonstrate that solution-sheared MAPbI3 - based perovskites are high performance and stable optoelectronic devices. The final research report takes a step towards creating environmentally friendly Sn-based perovskites in the ambient environment, an essential step to keep costs low. Sn perovskites are usually made and stored in inert atmospheres with less than 0.1 ppm oxygen. In the final research report, 2D Sn perovskites are created in the ambient environment and the ThMA molecule again results in the best films further cementing its superiority over the ubiquitous phenylethylammonium (PEA) and butylammonium (BA). Fundamental effects of H2O and O2 on the Sn perovskite crystal lattice are demonstrated on novel Sn perovskites, including more crystal defects, lattice expansion and disordered crystallization. This final report will be instrumental in understanding how to make Sn perovskite photodetectors in a feasible way to protect human health and the environment from Pb. This thesis will lead to the creation of environmentally friendly, efficient, and stable perovskite photodetectors with applications that benefit society in a safe way.