Ultrathin polymer layer boosts perovskite solar cell efficiency to 26.39%

A team of solar engineers at Huaqiao University, working with a pair of chemists from the City University of Hong Kong and another colleague from the Chinese Academy of Sciences, has developed an improved perovskite solar cell with 26.39% efficiency. In their study, published in Nature Communications, the group used a hole-selective interlayer that inhibits ion diffusion to improve the device’s stability.

Over the past several years, scientists have been looking for ways to replace silicon as the basis for solar cell production due to its complex and expensive manufacturing process. The most promising replacement is the mineral perovskite, which is made up mostly of calcium titanate. But it has some hurdles to overcome, such as durability, scalability, its environmental impact and, of course, its cost.

Convinced that research efforts will soon overcome such problems, scientists continue to improve perovskite solar cell efficiency so that once they are ready for use, they will be efficient enough as well. In this new study, the team in China claims that their new approach overcomes the inherent instability of perovskite cells due to ion migration.

The researchers created a super-thin p-type polymeric layer using a spin coating of PDTBT2T-FTBDT, which they call D18. In testing, it exhibited strong ion-blocking abilities between a layer of perovskite and the hole transport layer. Holes in solar cells refer to positively charged particles that are generated by light absorption—they serve as guides toward the anode.

Further testing showed that the D18 layer installed in a functioning solar cell inhibited ion diffusion between layers as intended—and worked better than other polymers they tried. They also showed that it improved the alignment of energy at the interface of the hole transport layer and the perovskite and successfully carried out efficient hole extraction.

Testing of the solar cell with the D18 installed showed it capable of achieving 26.39% efficiency with an aperture area of 0.12 cm². They also noted that the solar cell was able to operate at 95.4% initial efficiency after running for 1,100 hours, demonstrating improvements in durability as well.

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