Investigation of Charge Dynamics of Bismuth Defects in Perovskite Solar Cells by Intensity-Modulated Photocurrent Spectroscopy
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Xiao, Xiangyu
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Abstract
Perovskite solar cells (PSCs) have gained significant attention due to their remarkable power conversion efficiency (PCE), ease of fabrication, and low cost. In the past decade, PSCs have achieved a PCE of 26.7%. However, understanding the fundamental mechanisms influencing their performance, such as charge carrier transport, recombination, and extraction, remains a challenge. While PSCs are often considered defect-tolerant, impurities such as bismuth (Bi) can significantly affect device efficiency. Previous studies have demonstrated that Bi impurities can create shallow and deep traps within the conduction band, affecting carrier dynamics. However, detecting recombination due to Bi impurities has proven difficult using traditional methods like impedance spectroscopy (IS) and transient photovoltage (TPV) decay. This work aims to use intensity-modulated photocurrent spectroscopy (IMPS) to investigate carrier dynamics with Bi impurities in PSCs. By varying the concentration of Bi in the perovskite precursor, devices with a concentration above a 0.5% Bimolar ratio show deep-trap characteristics in the imaginary component of IMPS, further proving the existence of trap-assisted recombination and related characteristics.
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Undergraduate Research Option Thesis