In recent years, researchers around the world have tried to develop solar panels and other technologies that can produce electricity from renewable sources, as they can reduce greenhouse gas emissions and thus help preserve life on our planet. Solar cells can be built using a variety of materials, including silicon, copper, or other semiconductors.
Another class of materials that have proven very promising for making solar cells are perovskites, minerals of calcium oxide and titanium that can be extracted from The earth's mantle in certain geographical regions. This includes two-dimensional Ruddlesden-Popper (RP) perovskites, which have a unique structure that can improve the device's environmental sustainability and optoelectronic properties without significantly reducing its efficiency.
As a rule, two-dimensional RP perovskites have several quantum wells (QWS) with a random distribution of the wells across the width, which can impair the thermodynamic stability of perovskite solutions . QoS are thin layers that restrict particles in a dimension perpendicular to the surface of a given layer in the device (for example, in a well-like space), without restricting movement in other dimensions.
Researchers from Nanjing technical University and other institutes in China recently created solar cells using two-dimensional layered perovskites with RP with phase-pure quantum wells and a single-well width. These solar cells, presented in a paper published in the journal Nature Energy, can achieve outstanding energy conversion efficiency that is largely conserved over time.
"We report phase-pure quantum wells with a single well width by introducing a molten salt spacer of n-butylamine acetate instead of the traditional halide spacer of n - butylamine iodide," the researchers wrote in their paper. "Due to the strong ionic coordination between n-butylamine acetate and the perovskite framework, a gel of a uniformly distributed intermediate phase can be formed."
The main difference between the solar cells developed by this group of researchers and other similar ones developed in the past is the introduction of a layer of molten salt of the n-butylamine acetate spacer, which replaces the halide pads with n-butylamine iodide, commonly used for making solar cells. on the basis of 2-D RP-perovskites. The strong ionic coordination between this newly introduced layer and the perovskites eventually allows the formation of a gel from compounds with a uniformly distributed intermediate phase.
This unique design makes it possible to obtain phase-pure films with quantum wells with vertically aligned microparticles. These advantages are crystallized in the corresponding intermediate phases, which can ultimately improve the stability of solar cells.
In a series of initial tests, the researchers found that the solar cells they created achieved an energy conversion efficiency of 16.25% and a high open voltage of 1.31 V. Moreover, they evaluated the solar cells in three different scenarios: after they were in an environment with 65 ± 10% humidity for 4,680 hours; after operating at 85 ° C for 558 hours; and when they were under constant light illumination for 1,100 hours. In all of these three cases, the efficiency of the cells decreased by less than 10%.
These results suggest that the limitations associated with quantum wells of previously developed perovskite-based RP solar cells can be overcome by introducing a molten salt separation layer. In the future, the unique design of solar cells presented in this recent article may allow the creation of solar panels or other solar-powered devices that are both efficient and stable.
"Compared to traditional fully inorganic quantum wells deposited using vacuum methods, hybrid organic-inorganic metal halide perovskite phase-pure quantum wells offer several improvements, including processability in solution, low - temperature fabrication, and accuracy of atomic layers," the researchers explained. paper. "Taking into account the good stability, unique structure, and optoelectronic properties, we expect phase-pure quantum wells to contribute to the development of solar cells and other perovskite-based optoelectronic devices such as detectors, LEDs, and lasers."