Research Background and Objectives
Organic-inorganic halide perovskite solar cells have significant potential in solar energy development because of their long diffusion length, high light absorption coefficient, and excellent charge mobility. Due to these characteristics, the power conversion efficiency (PCE) of perovskite solar cells has rapidly increased from 3.8% to 26%. However, using lead (Pb) poses environmental and health risks, limiting commercialization. Therefore, active studies are being conducted on lead-free perovskite materials that maintain high efficiency while using less harmful substances.
Alternative materials such as tin (Sn), germanium (Ge), antimony (Sb), bismuth (Bi), and copper (Cu) have been proposed. Among them, tin is considered a promising candidate to replace lead due to its high charge mobility, low exciton binding energy, and suitable bandgap. However, tin-based perovskites suffer instability and low efficiency (below 15%) caused by oxidation and strong self-doping. This study aims to improve structural stability and PCE by introducing additives to overcome these limitations.
Experimental Methods and Procedures
In this study, we introduced various additives to improve the performance of tin-based perovskite solar cells, aiming to enhance grain growth and charge carrier mobility. The additives used in the experiment were bromides and various organic amine compounds, which were added to the precursor solution in small amounts. These additives were selected to help the vertical orientation of tin-based perovskite films and to increase grain size for charge recombination reduction and conductivity enhancement.
Solar cell thin films were fabricated through spin coating and annealing, and solvent evaporation and crystallization were processed without anti-solvent treatment. Subsequently, we analyzed electrical characteristics to evaluate the efficiency and stability of the films with additive introduction and conducted the X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses in parallel to determine the crystal structure and defect states.
Analysis Methods
To comprehensively analyze the effects of additives on tin-based perovskites, we applied synchrotron radiation analysis. In particular, small-angle X-ray scattering (SAXS) was used to investigate the effects of introducing additives on grain growth and structural orientation within the film. In addition, we observed the surface and cross-section of the film with an electron microscope to identify microstructural changes caused by introducing additives. Furthermore, to evaluate electrical characteristics, we measured open-circuit voltage (V_OC), short-circuit current density (J_SC), fill factor (FF), and PCE.
Read more on PAL website