Abstract
Despite the remarkable progress in perovskite solar cells (PSCs), their instability and rapid degradation over time still restrict their commercialization. A 2D capping layer has been proved to overcome the stability issues; however, an in-depth understanding of the complex degradation processes over a prolonged time at PSC interfaces is crucial for improving their stability. In the current work, we investigated the stability of a triple cation 3D ([(FA0.83MA0.17)Cs0.05]Pb(I0.83Br0.17)3) and 2D/3D PSC fabricated by a layer-by-layer deposition technique (PEAI-based 2D layer over triple cation 3D perovskite) using a state-of-art characterization technique: electrochemical impedance spectroscopy (EIS). A long-term stability test over 24 months was performed on the 3D and 2D/3D PSCs with an initial PCE of 18.87% and 20.21%, respectively, to suggest a more practical scenario. The current-voltage (J-V) and EIS results showed degradation in both the solar cell types; however, a slower degradation rate was observed in 2D/3D PSCs. Finally, the quantitative analysis of the key EIS parameters affected by the degradation in 3D and 2D/3D PSCs were discussed.
Highlights
Perovskite materials are one of the most trending contemporary photovoltaic research topics due to their rapidly evolving performance, which has already reached very close to commercialized thin-film silicon solar cells
The difference in Voc of both the solar cell types was insignificant, and a similar observation was made in our previous work [28]
Omitted the need to add an extra R|C for 2D/3D sample fitting and seems more realistic. It was observed from the electrochemical impedance spectroscopy (EIS) results that the higher frequencies (HF) impedance of 3D and 2D/3D perovskite solar cells (PSCs), which is attributed to charge transfer resistance at the Au/HTM/perovskite interface, clearly increases with aging
Summary
Perovskite materials are one of the most trending contemporary photovoltaic research topics due to their rapidly evolving performance, which has already reached (at above 25%) very close to commercialized thin-film silicon solar cells. The addition of Cs to FA/MA cation results in the effective tuning of tolerance factor, and the resultant triple cation perovskite demonstrates enhanced performance and stability [11]. Phenylethyl ammonium (PEA+) and butylammonium (BA+) are the most commonly studied organic cations in 2D perovskites [5], and they have demonstrated an impressive enhancement in the performance and stability of PSCs. PEA+ is a bulky cation with a large radius that isolates the anionic layers of the 3D structure, transforming it into a 2D perovskite [17]. Further comprehensive understanding of the interfacial processes at the 2D/3D heterojunction is yet to be developed [26] Such an exciting direction of study can be critical in identifying fundamental degradation mechanisms, charge recombination, and built-in voltage losses and bringing improvements to PSCs’ performance and long-term stability. The 2D layer improves the interface by deposing a uniform 2D layer over it
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