Organic-inorganic halide perovskite materials have excellent optical capture capacity and carrier conductivity. Perovskite solar cells, with amazing power conversion efficiency, show great application prospects. However, a large number of unfavorable defects, growing up after or during annealing process due to their ionic nature, would lead to sites of nonradiative recombination and accelerate degradation of device efficiency and stability.

A research team lead by PAN Xu from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS), cooperating with ZHENG Haiying from Anhui University, have achieved high-efficiency perovskite solar cells by passivating interface defects using new-type low-dimensional perovskite. Related work has been published on ACS Energy Letters.

The researchers passivated and stabilized the perovskite light absorbing layer with amphoteric heterocyclic cation, and designed a new-type low-dimensional perovskite passivation layer.

They found that the new perovskite, due to its amphoteric properties and strong molecular interaction, was able to deal with different surface-terminating ends and exhibited a variety of passivation effects.

According to the theoretical calculation of defect formation energy, the formation of lead-based defect was effectively inhibited. The modified perovskite solar cells displayed reduced defect density and lowered nonradiative recombination, thereby resulting in a power conversion efficiency of over 24%.

Besides, the long-term stability against humidity, high temperature and light was improved.

This work indicates a direction for the directional management of interface defects during the practical application of perovskite photovoltaic devices.

It was supported by the China Postdoctoral Science Foundation, the Anhui Province Natural Science Foundation, and the CASHIPS Director's Foundation, among others.

a. Theoretical calculation model; b. the formation energy (△Hα) of interface defects; c,d. Defect density calculation and photovoltaic performance test of perovskite solar cells. (Image by LIU Guozhen)