This review presents the progress of the change of the PSK structure from 3 dimensional CH3NH3PbX3 to mixed cations or halides based PSKs and finally to Ruddlesden–Popper PSK two dimensional (2D) homologous structures regarding the lifetime improvement.

Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) reached up to 23%, their short lifetime and fast degradation still remain as the main challenges. In this work, a new facile optical method based on the high power UV-irradiation is presented for the recovery of the degraded PSCs. Addition to the full recovery of the performance, about 20% PCE enhancement and hystersis reduction are also achieved by UV-irradiation. UV-treatment causes modifications in both the bulk properties of the perovskite layer and the energy equilibrium at the interfaces. It is shown that UV-treatment effectively passivates the surface and grain boundaries defects in different types of the devices comprising normal and inverted configurations that is confirmed by the reduction of the density of defect states (DOS). It is proposed that UV-light passivates the shallow and deep defects by dissociation of adsorbed hydroxyl groups and water molecules during the device storage.

Organic−inorganic halide perovskites have shown great promise as photovoltaic materials that bridge the gap between facile and low-cost fabrication and exceptional solar cell performance. Manipulation of the stoichiometry and chemistry of the precursors is among the main techniques for controlling the structural properties of perovskite layer. Herein we report that when a precursor solution containing excess cation halides (CH 3 NH 3 I) is utilized for perovskite formation, in situ dissociation of cations (CH 3 NH 3 + ) occurs. The excess iodide ions(I − ) mostly participate in the formation of iodoplumbate complexes such as PbI 3 − and PbI 4 2−. It is shown that the released energy from the crystal formation reaction can dissociate the free CH 3 NH 3 I molecules and iodoplumbate complexes into smaller molecules such as CH 3 I and NH 3 . When the I − concentration in the precursor is increased, more complexes are formed and subsequently more dissociations occur. The produced components are mostly trapped in the perovskite crystals and can act as defects.

No abstract

No abstract