Solar cells made of lead halide perovskites have increased
in popularity during the last several years due to the many benefits that they
provide. These benefits include high optical absorption coefficients, long
carrier lifetimes, efficient transport properties, and tunable band gaps across
the solar spectrum. Arguably, the most important quality that the perovskites
possess is the low-cost synthesis process. Many studies have been done to
pinpoint the exact cause of the success of the lead based perovskite cells.
There are differing opinions on whether or not the perovskite layer is solely
responsible for the solar power effect, or if it works in unison with other
materials. Researchers have been working on ways to improve long-term
stability of perovskite cells. The current problem they are facing is the quick
degradation of cells when placed in certain conditions. To summarize a complex
issue, solar cells made with perovskite materials were more likely to degrade
over time due to light, applied bias, and ambience. Experiments were
performed to see effects of optical properties, luminescence, and air-exposure
on perovskite solar cells. The trials were repeated in order to ensure that the
product would be commercially reproducible. Relevant results include the
discovery that air exposure caused reversion to precursors, although steady
photoluminescence was shown to improve carrier lifetime in ambient conditions.
Behaviors that were observed experimentally can be explained by the
decomposition process of methyl-ammonium lead iodide.