A team of researchers from China's Tsinghua University, National Center for Nanoscience and Technology and Switzerland's Institute of Computational Physics (ICP) of the ZHAW School of Engineering have proposed a strategy to reduce defects and microstrains in perovskite films through multifunctional additives, achieving a record PCE of 23.6% for single-junction flexible perovskite solar cells (FPSCs).
Flexible perovskite solar cells (FPSCs) prepared on flexible substrates, which possess excellent flexibility and a high power-to-weight ratio, hold promise as a power source for wearable electronic devices, aerospace, and building integrated photovoltaics (BIPVs). Further improving the power conversion efficiency (PCE) and bending resistance of flexible devices is key to promoting their practical application.
In their work, the scientists introduced a succinate additive into the perovskite precursor to improve the quality of perovskite films and the performance of perovskite solar cells. The carboxylic acid group in the succinate anion can interact with the formamidinium cation via hydrogen bonding, and can coordinate with the dangling lead atom in the perovskite lattice. Methylammonium cations can fill cation vacancies on the surface of perovskite grain. These various interactions lead to the suppression of defect states in the perovskite film and the relaxation of microstrains, resulting in a high-quality perovskite film for photovoltaic applications.
The perovskite solar cells prepared using this method reportedly showed excellent photovoltaic performance. A PCE of 25.4% was achieved for rigid PSCs under AM 1.5G standard illumination. The FPSCs fabricated on flexible substrates achieved the highest PCE of 23.6% (certified of 22.5%), which was both the highest efficiency record for single-junction FPSCs reported and certified thus far. Meanwhile, more than 20% PCE has been achieved for flexible devices with an aperture area of 1 cm2.
In addition to performance enhancement, the addition of additives strengthens the grain of the film, which greatly improving the bending resistance of perovskite film. The flexible device still maintained 85% of the initial PCE after 10,000 bending cycles at a bending radius of 6 mm.
This work provides a new approach by using a multifunctional organic additive to strengthen the grain boundaries and heal defects in the perovskite film used for high-performance FPSCs. The excellent efficiency and bending resistance exhibited presents a promising future for FPSCs in practical application. The team plans to further focus on module design and stability enhancement to promote the development and applications of FPSCs.