| Work Detail |
Researchers from Germanys Fraunhofer ISE have provided guidelines for future research on perovskite-silicon tandem solar cells by identifying the most significant loss mechanisms at the perovskite/ETL interface, in series resistance and in light management.
A group of researchers at Germanys Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) has calculated that the practical power conversion efficiency potential of perovskite-silicon tandem solar cells can reach up to 39.5%.
“The calculated practical efficiency potential of 39.5% for a perovskite silicon tandem device under standard measurement conditions (STC) can serve as a basis for future research and development studies, necessary to better understand the complete system before commercialization of the promising tandem solar cell technology,” the corresponding author of the research, Oussama Er-raji, told pv magazine .
“In this work we have exhaustively characterized a fully textured perovskite silicon tandem solar cell to determine its performance losses,” explains Christoph Messmer, co-author of the work. “By implementing the extracted features of the device in a Sentaurus TCAD simulation model, we obtained a reproduction of the optical and electrical characteristics of the experimental device. Subsequently, by easing the loss constraints step by step, the simulation model identified the impact of each loss channel on efficiency.”
Sentaurus CAD is a multidimensional simulator capable of simulating the electrical, thermal and optical characteristics of silicon-based devices. It is also used to simulate the optoelectronic characteristics of semiconductor devices such as image sensors and photovoltaic cells.
In the study “ Loss Analysis of Fully-Textured Perovskite Silicon Tandem Solar Cells: Characterization Methods and Simulation toward the Practical Efficiency Potential ” of Practical Efficiency), published in RRL Solar , the research team claims to have investigated voltage, current and fill factor deficiencies in a fully textured perovskite silicon tandem solar cell based on an indium tin oxide recombination layer (ITO) of 20 nm thickness placed between the upper and lower cells.
The subcell was based on a 630 nm thick perovskite absorber with an energetic bandgap of 1.67 eV, a carbazole (2PACz) layer, a 20 nm thick tin oxide (SnOx) buffer layer, a electron transport technology (ETL) based on a buckminsterfullerene (C60), an ITO window layer, a silver (Ag) metal contact and an anti-reflective coating based on magnesium fluoride (MgF2). “The fully textured perovskite silicon tandem solar cell offers a stabilized PCE of 26.7% when operated at a fixed voltage close to the maximum power point,” the researchers state.
The scientists carried out a comprehensive loss analysis on the tandem device taking into account the high series resistance, current mismatch in the subcells, high non-radiative recombination losses, and band misalignment at the absorber interface. of perovskite and the ETL.
They identified the most significant loss mechanisms in the perovskite/C60 interface (-4.6%), in series resistance (-2.9%), and in light management (-2.1%). “By reducing the origins of these losses step by step, we calculate efficiency improvements by cumulatively mitigating the characterized loss channels, ultimately reaching a practical efficiency potential of 39.5% for this device architecture,” they explained.
The researchers also noted that the 39.5% efficiency threshold can only be overcome by changing the architecture of the cell, eventually replacing C60 with a more transparent ETL and finding more transparent alternatives to ITO layers. “Although this analysis shows a fairly idealized scenario for resolving device limitations, it is still useful to evaluate the ideal efficiency increase for each limitation,” they stressed. |
