Impedance Spectroscopy Analysis of solution-processed semiconductor photovoltaics

Abstract

This research project utilises impedance spectroscopy to investigate the electrical properties of solution- processed semiconductors. With their high absorption coefficient, rapid charge carrier mobility, and cost- effective production, such as perovskite materials1 have emerged as promising candidates for various electrical applications. However, their inherent flaws and instability hinder their effectiveness2. Impedance spectroscopy, a non-invasive and highly sensitive technique, enables the detailed examination of these materials' electrical characteristics and identification of performance-affecting defects. The outcomes of this study aim are to investigate the impedance spectroscopy for both an Organic (molecular semiconductors: P3HT/PCBM system) and Quantum Dot (colloidal semiconductor nanocrystals: PbS) solar cells. Impedance spectroscopy serves as a valuable tool for clarifying the defect characteristics and charge carrier dynamics of semiconductor devices, potentially facilitating insights into charge carrier transport and recombination mechanisms3 . By deriving essential electrical properties such as capacitance, resistance, and time constants from impedance spectra, it is possible to enhance the understanding of the electrical behaviour of solution- processed solid-state perovskite, organic semiconductor and colloidal quantum dot materials, which have attracted significant interest for their potential applications in solar cells, LEDs, and other electronic devices. Notably, very recently, solution-processed solid-state perovskite materials exhibit improved stability, compared to their liquid counterparts, making them more suitable for device integration4. Through impedance spectroscopy analysis of their electrical characteristics, this study aims to identify and mitigate flaws affecting the performance of these materials and enhance device efficiency5 . Organic and Quantum Dot materials show promise for manufacturing applications due to their varying impedance characteristics under dark and light conditions. This pertains to the transfer of charges at the p-n junction6,7 .