Tandem solar cells (TSCs) comprise two stacked layers, with each subcell absorbing different wavelengths of sunlight, which makes TSCs more efficient than single-layer solar cells.
All-perovskite TSCs hold great promise for next-generation photovoltaics, with a theoretical efficiency exceeding 40%. However, their practical performance is hampered by mismatched crystallization kinetics between their wide-bandgap (WBG) and narrow-bandgap (NBG) subcells, leading to phase segregation and defect accumulation.
To address this challenge, a research group led by Prof. GE Ziyi and Prof. LIU Chang from the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences developed an innovative colloidal chemistry strategy to enhance the performance of these TSCs, achieving a power conversion efficiency (PCE) of 29.76%.
The study was published in Joule on March 27.
The researchers designed a unified carboxylate-based modulator system using two graded carboxylate anions—tartrate (Ta - ) and citrate (Cit - )—to precisely regulate the nucleation dynamics of the two subcells.
In the WBG subcell, Ta - stabilizes Pb 2+ coordination, suppressing phase segregation and promoting uniform crystal growth. Cit - , meanwhile, optimizes Sn-I bonding in NBG colloids, passivating (turning off) Sn 2+ defects and enhancing charge transport. Choline cations further synergize with these modulators, passivating undercoordinated metal ions at crystal-colloid interfaces to form a robust stabilization matrix.
With this integrated strategy, the optimized tandem device achieved an impressive PCE of 29.76%, with a certified value of 29.22%. The device also demonstrated strong operational stability, retaining more than 90.2% of its initial efficiency after 700 hours of continuous operation under maximum power point tracking.
Notably, the 1 cm 2 large-area tandem cell delivered a high PCE of 28.87%, highlighting the scalability of the colloidal chemistry strategy.
The researchers note that this work provides a universal approach to harmonize multijunction crystallization, paving the way for the commercialization of high-efficiency all-perovskite tandem solar technologies.
The study was supported by the National Key Research and Development Program of China, the Young Scientists Fund of the National Natural Science Foundation of China, and the National Natural Science Foundation of China, among others.
Joule
Experimental study
Not applicable
Tailoring Colloidal Precursor Chemistry for Tunable Nucleation Kinetics in All-Perovskite Tandem Solar Cells
27-Mar-2026