Unravelling the electrochemical impedance spectroscopy of hydrogenated amorphous silicon cells for photovoltaics

Materials for Renewable and Sustainable Energy https://doi.org/10.1007/s40243-024-00295-2 (2025) 14:17 ORIGINAL PAPER Unravelling the electrochemical impedance spectroscopy of hydrogenated amorphous silicon cells for photovoltaics Soni Prayogi1,3 · Deril Ristiani2,3 · D. Darminto3 Received: 12 June 2024 / Accepted: 29 December 2024 © The Author(s) 2024 Abstract This research reveals the application of electrochemical impedance spectroscopy (EIS) in analyzing and improving the performance of hydrogenated amorphous silicon (a-Si: H) based photovoltaic cells. As a non-destructive technique, EIS provides deep insight into the electrochemical characteristics of photovoltaic cells, including series resistance, layer capacitance, recombination mechanisms, and charge transport. The impedance data is obtained and analyzed using small AC potential signals at various frequencies via Nyquist diagrams and Bode plots. This analysis allows the identification of resistive and capacitive elements as well as the evaluation of the quality of the interface between the active layer and the electrode. The results show that EIS can identify internal barriers that reduce the efficiency of a-Si: H solar cells, such as dominant recombination mechanisms and inefficient charge transport. Using equivalent circuit models, electrochemical parameters are extracted to reveal cell behavior and performance. In addition, these results also confirm that EIS is an important tool in design optimization and performance improvement of a-Si: H photovoltaic cells, providing a solid scientific basis for the development of more efficient and sustainable solar cell technology. These findings contribute to efforts to increase solar energy efficiency, supporting broader and more effective use of photovoltaic technology in meeting global sustainable energy needs. Keywords a-Si: H · EIS · P-i-n · Photovoltaic Introduction In recent decades, ever-increasing global energy needs have driven research and development of renewable energy technologies [1]. One technology that stands out in terms of its potential and applications is photovoltaics, which converts sunlight directly into electricity using solar cells [2]. Among the various types of solar cells that have been developed, hydrogenated amorphous silicon (a-Si: H) cells are of particular interest due to their advantages, such as low production Soni Prayogi 1 Department of Electrical Engineering, Pertamina University, 12220 Jakarta, Indonesia 2 Nanotechnology Research Center, National Innovation Research Agency, 10340 Jakarta, Indonesia 3 Advanced Materials Research Group, Department of Physics, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia costs, material flexibility, and the ability to be synthesized at low temperatures [3]. However, although a-Si: H technology offers significant advantages, the relatively low energy conversion efficiency compared to crystalline silicon cells remains a major challenge to be overcome [4]. The a-Si: H photovoltaic cell has a structure consisting of several thin layers, including the p-i-n layer which functions as a charge generator and collector [5]. In operational processes, various physical and electrochemical phenomena influence cell performance, such as charge carrier recombination, charge transport, and interface effects [6]. To optimize the design and performance of a-Si: H solar cells, a deep understanding of these mechanisms is essential [7]. Electrochemical impedance spectroscopy (EIS) is emerging as a very useful tool in this regard [8]. EIS is an analytical technique that allows detailed characterization of electrochemical parameters in a non-destructive manner, making it very suitable for the research and development of photovoltaic cells [9]. Electrochemical impedance spectroscopy involves applying a small AC potential signal to a system and measuring the resulting current response at various frequencies 13 17 Page 2 of 10 [10]. By analyzing this response, EIS can reveal important parameters such as series resistance, layer capacitance, and recombination mechanisms that occur within the solar cell [11]. Nyquist diagrams and Bode plots are two common data representations used for the interpretation of EIS results [12]. The Nyquist diagram depicts the relationship between the imaginary and real parts of the impedance, while the Bode plot shows the changes in impedance and phase as a function of frequency [13]. Through the interpretation of appropriate circuit equivalent models, the electrochemical parameters of solar cells can be extracted to provide insight into charge transport and recombination processes [14]. The use of EIS in the characterization of a-Si: H photovoltaic cells offers several advantages [15]. This technique not only allows in-depth analysis without damaging the device but can also be carried out in operational conditions close to reality, making the results obtained more relevant to cell performance in the field [16]. Additionally, EIS can identify the contribution of various elements in the system, such as ohmic contacts, active layers, and interfaces between layers, all of which play an important role in the overall efficiency of the device [17]. Thus, EIS not only helps identify key bottlenecks in solar cells, but also provides valuable guidance for design and material improvements [18]. Although EIS offers many benefits, interpretation of EIS data remains challenging due to the complexity of the electrochemical system in a-Si: H solar cells [19]. Circuit equivalent models used to fit experimental data must accurately reflect the physical phenomena occurring within the cell, which requires a deep understanding of electrochemical mechanisms [20]. Additionally, variability in solar cell manufacturing and measurement conditions can also influence EIS results, so data analysis must be performed carefully to ensure its validity and reproducibility [21]. This research aims to explore the use of EIS in the characterization of a-Si: H photovoltaic cells, with a focus on uncovering critical electrochemical parameters for cell performance improvement. Through this study, it is hoped that a better understanding of the mechanisms of charge transport and recombination in a-Si: H cells can be obtained, as well as identification of the main obstacles that reduce energy conversion efficiency. Thus, the results of this research will contribute to the development of more efficient and reliable a-Si: H solar cells, supporting global efforts to develop sustainable and economical renewable energy technologies [22]. In this study, we will present the methodology used to measure and analyze EIS data, as well as results and discussion related to the electrochemical characterization of a-Si: H photovoltaic cells. 13 Materials for Renewable and Sustainable Energy (2025) 14:17 Experiment Method Electrode preparation Electrode preparation for EIS on a-Si: H cells is a crucial step that d (...truncated)