Study of stability of hybrid perovskites by methods of weak absorption measurement

Since 2014, when we showed that the sharp absorbing edge of hybrid perovskite is a generally valid argument for high material quality, we have been dealing with the stability effects observed by the absorption methods. Apart from the transformation of the hybrid perovskite CH₃NH₃PbI₃ into PbI2 due to degradation, we have shown that the two-phase system CH₃NH₃PbI₃ - PbI2 has specific properties supporting the hypothesis of efficient transfer of holes from the PbI₂ phase to CH₃NH₃PbI₃ grains. Another effect of PbI2 is its decomposition and release of iodine, which diffuses into the perovskite grains and induces interstitial deep defect levels, which can be detected by very low absorption below the edge of the band gap.