Bulk Heterojunction Unleashes Potential of Cs-based Perovskite Solar Cells

Solar cells can directly convert light energy into electrical energy through photoelectric effect or photochemical effect. Metal halide perovskites solar cells (PSCs) have attracted tremendous attention, owing to their excellent optical and electrical properties.

Among these metal halide PCSs, cesium (Cs)-based PSCs are very promising due to excellent thermal stability. However, Cs-based perovskite devices suffer from severe open-circuit voltage loss, which limits the advantage of the wide-bandgap and seriously affects their power conversion efficiency (PCE).

To combat these problems, a research team from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) has proposed a strategy to accelerate carrier transport and collection in Cs-based PSCs and improve the device performance.

Their study was published in Joule on March 3.

Cs-based PSCs, especially CsPbI3 PSCs, are far below the Shockley-Queisser limit, which is mainly caused by the large open-circuit voltage loss resulted from the severe carrier non-radiative recombination. "We think that constructing heterojunction inside perovskite film should be a very interesting strategy to reduce carrier recombination loss," said Prof. PANG Shuping from QIBEBT, the corresponding author of the study.

Dr. SHAO Zhipeng, author of the paper, said "Small amount A-site cation doping in Cs-based perovskite materials can significantly change its energy band structure and electrical properties, which is the basis for realizing heterojunction in the perovskite films."

Experiment found that perovskite heterojunction was achieved by precisely controlling of phase composition, which significantly accelerates the separation and transmission of photogenerated carriers. "And more importantly, this direct transformation inside the film is very easy to implement," said the first author SUN Xiuhong.

The voltage of Cs-based PSCs has been highly improved. "It is a milestone to achieve 20% PCE through constructing bulk-heterojunction in Cs-based PSCs," said Prof. CUI Guanglei from QIBEBT. "This improvement also brings dawn for Cs-based PSCs to be used as tandem solar cells."

Schematic illustration of the carrier transport in bulk heterojunction PSCs. (Image by SUN Xiuhong)

(Text by Shao Zhipeng)



Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences

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