2021 Science Advances: Challenge the performance limitations of WBG mixed halide perovskites!
Top-Notch Due to It’s Precision!
Science Advances (IF 14.136) published the research results of Yang Yang from University of California Los Angeles (UCLA) , Carolin M. Sutter-Fella from Lawrence Berkeley National Laboratory and Ilhan Yavuz from Marmara University etc. in November 2021. In the past, it has been proven that metal halide perovskites, if their X-sites of iodine partially substituted with bromine, have great commercial potential and can be applied to tandem photovoltaics (PVs) integrated with conventional PV products, such as: Si and CuInGaSe2 (CIGS). By controlling the I/Br ratio, the optical bandgaps of the mixed-halide perovskites can be adjusted to between 1.64 and 1.70eV. It is usually called wide-bandgap (WBG) perovskite in this field, which is very suitable for front-cell applications in two-junction tandem PVs. Use this WBG mixed-halide perovskite as the front cell absorber to realize perovskite-based tandem solar cells with over 29% power conversion efficiency. However, their large voltage deficits limit their ultimate performance. At present, only a few studies have explored the problem of voltage deficits, and this is also an unsolved challenge in this field. In this study, the authors studied the formation dynamics and defect physics of WBG mixed-halide perovskites in contrast with their corresponding triiodide-based perovskites.
Abnormal formation dynamics in WBG mixed-halide perovskites.
Enlitech’s QE-R Quantum Efficiency Measurement system and other instruments were used in this study to assist in the measurement. As a result, it was found that the inclusion of bromide in the composition changed the perovskite crystallization pathway. The bromide-rich phase was more thermodynamically stable, so nucleates first from solution during supersaturation. To achieve the final target stoichiometry, halide homogenization was achieved during the perovskite growth stage. A physical model was further clarified, which relates the role of bromide with the formation dynamics, defect physics, and eventual optoelectronic properties of the film. This research will lead the community to rethink the significance of precursor engineering and crystallization control for WBG mixed-halide perovskites to achieve more efficient and stable PVs based on these materials.
The quantum efficiency measurement system is used for EQE (external quantum efficiency) spectral analysis of perovskite solar cells. It also provides a comparison of Jsc (short-circuit current density) for the short-circuit current of solar cells under sunlight to verify the experimental results.
In situ PL measurements monitoring the formation kinetics of perovskite films.
Solar cell devices and the proposed physical model. J-V characteristics (A) and EQE spectrum (B) of perovskite solar cell devices based on CsFAMAPb(I0.8Br0.2)3 and CsFAMAPbI3.