A team of engineers in China has achieved a new milestone in photovoltaics by creating a tandem solar cell entirely made of perovskite with a conversion efficiency of 28.49%
A new breakthrough in photovoltaic technology has emerged from China. Engineers at Huazhong University of Science and Technology have developed a 100% perovskite tandem solar cell with the highest conversion efficiency in its category—an impressive 28.49% (independently verified). Moreover, the unit demonstrated excellent operational stability, maintaining high performance even after 550 hours of continuous operation.
The Shockley-Queisser Limit for Perovskite Photovoltaics
In the past decade, perovskite solar cells have made significant advancements, achieving a conversion efficiency of 26.7% in single-junction architectures. However, while efforts to improve performance in this area continue, some researchers are already exploring ways to surpass the Shockley-Queisser limit.
Also known as the radiative efficiency limit, this factor represents the maximum theoretical efficiency that a solar cell using a single pn junction can achieve, where the only loss mechanism is radiative recombination. For perovskite solar cells, this limit is estimated to be around 31%.
One potential approach to exceed this limit is through tandem solar cell technology, which involves stacking multiple layers with different bandgaps to capture a broader spectrum of sunlight and enhance overall efficiency.
Multijunction Solar Cells
One way to overcome the Shockley-Queisser limit is through multijunction technology, which utilizes two or more different photovoltaic materials with varying bandgaps. Typically arranged in a monolithic architecture, the solar cells at the top of the tandem stack feature a wide bandgap, converting UV and blue light into electricity, while the lower cells have smaller bandgaps and capture red and IR light. This combination allows for significantly higher conversion efficiencies than single-junction cells.
Perovskites hold a particular advantage in this field: unlike other photovoltaic semiconductors, their bandgap can be pre-tuned to different wavelengths. This capability enables creating tandem solar cells made entirely of perovskite, with each subcell optimized for a specific spectrum region.
The main challenge? Surface defects caused by non-radiative recombination losses in smaller bandgap perovskite films hinder efficiency.
Record-Breaking Tandem Solar Cell in Perovskite
Research from Huazhong University of Science and Technology has made a significant contribution to this area. A team of scientists developed a technique to reduce surface defects in perovskite films. Specifically, they used a surface polishing agent, 1,4-butanediamine, combined with a surface passivator, ethylenediammonium diiodide, to eliminate or suppress these defects. This improvement enhanced charge carrier transport and reduced non-radiative energy losses.
The team created two perovskite subcells with bandgaps of 1.32 and 1.25 eV, achieving power conversion efficiencies of 22.65% and 23.32%, respectively. The tandem solar cell, composed of these two junctions, reached a certified conversion efficiency of 28.49%. The study was published in Nature Communications.
