Chinese scientists have found a new way to extend the life of perovskite solar cells
Xinhua News Agency, Shanghai, March 7 (Reporter Wu Zhendong) Compared with crystalline silicon cells, perovskite solar cells have the advantages of high conversion efficiency, low cost, and light weight. They are a new photovoltaic technology with great application prospects, but the instability of the device is the primary challenge limiting its industrialization.
The reporter learned from East China University of Science and Technology that a study by the school's clean energy materials and devices team found that the "photomechanically induced decomposition effect" is the key mechanism of new photovoltaic instability, and proposed a new method of graphene-polymer mechanical enhancement of perovskite materials. The new device prepared based on this method broke the "short-lived" curse of perovskite solar cells. The research provides a new solution for the industrialization of perovskite solar cells, and the relevant results were published in the journal Science on the 7th.
Perovskite materials are the key components of perovskite solar cells. The "photomechanically induced decomposition effect" refers to the dynamic local stress inside the material that induces the decomposition of the material. Professor Hou Yu, the head of the research team, introduced that under sunlight, perovskite materials show a significant photostrictive effect, and the expansion ratio can exceed 1%, which will lead to the squeezing of perovskite crystals and the accumulation of local stress near the grain boundaries, accelerating the formation of defects in the grain boundary area, causing the performance loss of perovskite cells.
To improve the stability of perovskite materials, scientists have previously tried various methods such as designing and controlling the molecular structure of the material surface, but it is still difficult to meet the needs of practical applications. The discovery of the "photomechanically induced decomposition effect" has brought new ideas to solve this problem.
It is reported that under the same external force, the deformation degree of graphene is only 1% to 2% of that of perovskite materials, and it has the advantages of uniform density, mechanical fatigue resistance and stable chemical properties. The stability of perovskite materials can be improved with the help of graphene. "Thanks to the excellent mechanical properties of graphene and the coupling effect of polymers, the graphene-polymer double-layer structure reduces the lattice deformation rate from +0.31% to +0.08%, effectively reducing the material damage caused by expansion near the grain boundaries." Hou Yu said.
Dynamic structural evolution experiments and model calculations confirm that this new type of perovskite solar cell device can effectively suppress lattice deformation and lateral ion diffusion under working conditions. For example, after working for 3670 hours under standard sunlight and high temperature, the device can still maintain more than 97% of its initial efficiency.
