Perovskite solar cells with a photoelectric conversion efficiency exceeding 27% have been successfully developed.

Reporters learned on the 10th from the Institute of Semiconductors, Chinese Academy of Sciences, that the research team led by Professor You Jingbi has made significant progress in the field of perovskite solar cells. They have developed a prototype perovskite solar cell with a photoelectric conversion efficiency of 27.2% and significantly improved its operational stability, laying a crucial foundation for the industrialization of perovskite solar cells. The relevant research results were published online in the journal *Science*.

Perovskite solar cells, as a novel photovoltaic technology, have seen their photoelectric efficiency rapidly increase from an initial 3.8% to over 26% in the past decade, but this still falls short of their theoretical limit. Achieving high efficiency hinges on the fabrication of high-quality perovskite thin films. Methylammonium chloride is widely used as an auxiliary material for perovskite thin film growth because it can simultaneously lower the perovskite nucleation barrier and promote high-quality crystal growth.

In this study, researchers discovered that in conventional processes, chloride ions from methylammonium chloride migrate and accumulate on the upper surface during thin film crystallization, leading to uneven chlorine distribution in the vertical direction of the perovskite layer. This inhomogeneity can cause surface defects and interfacial electronic barriers, increasing carrier recombination and affecting battery performance and long-term stability.

To address this problem, researchers proposed a strategy to achieve a uniform distribution of chloride ions in the vertical direction. They introduced alkali metal oxalate during film growth, utilizing the strong binding effect between the potassium ions released from oxalate and chloride ions to effectively suppress the disordered migration of chloride ions, thus ensuring their uniform distribution within the perovskite layer.

The perovskite thin films prepared using this method show significantly improved quality: carrier lifetime is extended to 20 microseconds, and interface defect density is greatly reduced. Solar cells based on this thin film have been certified by multiple authoritative institutions, achieving a photoelectric conversion efficiency of 27.2%. In terms of stability, the cells retain 86.3% of their initial efficiency after 1529 hours of continuous operation; and maintain 82.8% of their initial efficiency after 1000 hours of accelerated aging under photothermal coupling at 85℃.

It is understood that this research has achieved a synergistic improvement in the efficiency and stability of perovskite solar cells, which will provide important support for promoting the industrialization of perovskite solar energy technology.