Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical and Aerospace Engineering


Qiao, Quinn


Additive, Lead free, Perovskite, Solar cell

Subject Categories

Mechanical Engineering


High-efficiency perovskite solar cells that are also very cheap to produce have been rapidly developed in response to the growing global demand for electricity. However, the light absorber materials used in cutting-edge perovskite solar cells include lead, which has been linked to health risks for people and other living organisms. Accordingly, the developing front in photovoltaic research is the discovery and development of new lead-free perovskite materials for the future global commercialization of non-toxic, stable, and efficient perovskite solar cells, by replacing hazardous lead with non-toxic metal elements in the same group as lead in the periodic table, lead-free PSCs have gained pace, with tin being the most promising because to its strong charge carrier mobility and the theoretical efficiency of Sn-based perovskites reaching approximately 30% due to their optimal smaller bandgap between 1.1 and 1.4 eV. Due to similar ionic radii and outermost electron configuration to Pb2+, Sn-based PSCs have been a magnet for significant rearrangement in the lead-free PSC community. However, Sn-based perovskites have poor stability and low efficiency in PVSCs because they oxidize and decompose quickly.Due to a lack of foundational knowledge of the Sn2+ compounds, it is yet impossible to fabricate high-quality Sn-based perovskite films. Due to these deficiencies, the potential for the related film qualities, such as smooth surface morphology, pinhole-free layer development, and low crystallinity, is hampered. The Sn-PVSCs with the best performance to date are those made with FASnI3 in the absorber layer. Inside the FASnI3 perovskite precursor, the reaction between Formamidine iodide (FAI) and SnI2 occurs rapidly. The increased reactivity of SnI2 as a Lewis acid contributes to this speedy interaction, which ultimately leads to rapid crystal growth with imperfect nucleation. There are many pinholes, poor crystallinity, and a high defect density in the films. The addition of Lewis bases to the Sn-perovskite precursor solution was proposed as a way to slow down the crystallization process by weakening the interactions between the precursors. In this thesis, to get high-quality perovskite for the manufacturing of highly efficient PVSCs, a Lewis base Thioacetamide (TAA) was utilized as an addition in the simple composition of FASnI3 perovskite solution. FASnI3 and TAA additive-based films effectively controlled the crystallinity and grain size of the perovskite films. The champion FASnI3+TAA-based perovskite device demonstrated the greatest 10.67% PCE while also being more stable. Furthermore, the TAA additive produced a dense, smooth, and high-quality perovskite film with increased short circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF), and PCE.


Open Access

Available for download on Monday, January 13, 2025