Researchers have unveiled impressive advancements in solar technology with the development of methylammonium-free all-perovskite tandem solar cells (APTSCs), showing significant improvements in both efficiency and stability. Central to this breakthrough is the use of rubidium acetate (RbAC) as a versatile additive, capable of enhancing the overall performance of these innovative solar cells.
All-perovskite tandem solar cells have emerged as promising contenders to exceed the Shockley-Queisser efficiency limit typically seen with single-junction solar cells. Traditionally, the integration of methylammonium (MA) has been common to improve performance; nevertheless, this compound has well-documented stability issues, with devices often degrading under continuous light exposure. By pivoting away from MA, researchers aimed to forge stronger and more durable solar cell technologies.
The crux of the study lies within the functionality of rubidium acetate. This additive not only facilitates the stabilization of the tin-lead (Sn-Pb) narrow bandgap (NBG) perovskite structures but also plays a pivotal role in suppressing oxidation of Sn2+, which can lead to inferior charge transport properties. According to the authors of the article, "The oxidation of Sn2+ to Sn4+...poses a significant challenge in achieving high-quality Sn-Pb perovskite thin films.”
Insights from this study reveal how the incorporation of RbAC prevents degradation phenomena associated with Sn2+ oxidation, thereby resulting in improved crystallinity and grain structural integrity within the perovskite films. Following rigorous analysis through Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy, the results indicated effective interactions between RbAC and undercoordinated Sn2+, showcasing the latter’s oxidative suppression capabilities.
Demonstrably, the adoption of RbAC led to significant improvements in carrier lifetime, with the lifetime statistics climbing from under one microsecond to 5.01 microseconds. With a reported power conversion efficiency (PCE) uptick to 23.02% for the Sn-Pb single-junction cells, the findings mark the highest efficiency for MA-free configurations documented to date. All-perovskite tandem devices, which integrated this MA-free Sn-Pb cell with another wide-bandgap (WBG) cell, achieved outstanding efficiencies of 29.33%, with certification stating 28.11%.
Additional data highlight how these perovskite solar cells maintain performances across various environmental conditions. The operational stability after sustained light exposure showed the target devices could maintain 80% of their initial PCE after 850 hours, far exceeding the control devices. The researchers also noted less susceptibility to thermal degradation when the cells experienced elevated temperatures. This multifaceted approach suggests potential for commercial viability as the world transitions to renewable energy sources.
By culminating efforts across various scientific fields, this research signifies monumental strides toward overcoming significant barriers traditionally associated with perovskite solar cells. The authors encapsulated this sentiment succinctly, stating, “This approach opens up avenues for enhancing the performance of MA-free photovoltaic devices.” With this innovation centered on RbAC, the path toward highly efficient, stable, and economically feasible solar technologies grows more tangible, heralding exciting prospects for consumers and the industry alike.