The research team at Alamos National Laboratory recently published a study on the photo-degradation process associated with perovskite solar cells and the surprising small solution to their degradation tendencies. The researchers were able to stabilize the devices by adjusting the temperature and light of the surroundings.
While standard solar cells lose as much as 50% of absorbed light energy, perovskite solar cells, which have a crystallographic structure of the perovskite mineral, lose far less energy and offer practical applications.
Perovskite solar cells are also economically favorable since the material is made through a low-temperature solution process. While their tendency to be favored in applications is obvious, the solar cells are undermined by sunlight and degrade in terms of a photocurrent.
Research showed that when placed in the dark for several minutes, the degraded solar cells essentially self-heal due to their properties. It was discovered that photo-degradation in perovskite cells, which happens from charge accumulation to the crystal structure, can actually be reduced.
Wanyi Nie, one of the lead researchers, stated, “The degradation of the devices can be suppressed by simply lowering the temperature by few degrees, that is, from 25 degrees Celsius to 0 degrees Celsius.”
Device and spectroscopy characterization showed that as charge accumulates the photocurrent reduces. Sunlight activates the meta-stable trap states at low energy deep in the bandgap, which leads to the trapping of photo-generated charge carriers. The explanation surrounding the origin of the formation of the trap states rests on experimental and theoretical evidence of lattice strain and molecular re-orientations of CH3NH3.
When the perovskite cells are placed in the dark, however, the trapped charges evacuate and upon the following operation cycle, the device performance recovers. The results provide a solution to maintaining stability in perovskite devices and propose an application to U.S. energy security needs.