A building of the Shanghai Jiao Tong University.
Image: wikimedia commons, Bwfrank
Researchers from Shanghai Jiao Tong University and the South China University of Technology have developed a single-layered organic solar cell based on non-fullerene acceptors with an efficiency of 16.88%.
The researchers said that they achieved this result with an efficient donor–acceptor mixture and a particular film morphology. They explained that the latter is crucial for improving the cell fill factor and short-circuit current density.
“Thermal annealing at moderate temperature helped to refine the crystalline order of Y6 in bulk heterojunction blends, yielding the global optimization in photovoltaic parameters,” the team said. Y6 is a highly conjugated organic semiconductor that is used as an acceptor for different organic cell technologies.
The scientists attributed the improvements to what they define as an optimized multilength scale morphology and unique 2D crystalline packing with tilted molecular geometry, which they claim is more suitable for vertical charge transport. “The results demonstrate that Y6 can form a unique 2D packing with a polymer‐like conjugated backbone oriented normal to the substrate, controlled by the processing solvent and thermal annealing conditions,” they stated.
This was confirmed by Pearson correlation analysis, which provides a measure of the strength of the association between the two variables. It revealed that the crystallinity of Y6 is the most important factor governing carrier mobility, which means that the new morphology improves carrier transport while also providing for an ultrafast hole and electron transfer.
The researchers have reported a certified efficiency rate of 16.4% for their cell, with the most-optimized device exhibiting an efficiency of 16.88%.
They presented the cell’s morphology in Efficient Organic Solar Cell with 16.88% Efficiency Enabled by Refined Acceptor Crystallization and Morphology with Improved Charge Transfer and Transport Properties, which was recently published in Advanced Energy Materials.
Source: PV Magazine – Emiliano Bellini