Organic–Inorganic Halide Perovskite Formation: In Situ Dissociation of Cation Halide and Metal Halide Complexes during Crystal Formation

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 (CH₃NH₃I) is utilized for perovskite formation, in situ dissociation of cations (CH₃NH₃⁺) occurs. The excess iodide ions­(I^–) mostly participate in the formation of iodoplumbate complexes such as PbI₃^– and PbI₄^2–. It is shown that the released energy from the crystal formation reaction can dissociate the free CH₃NH₃I molecules and iodoplumbate complexes into smaller molecules such as CH₃I and NH₃. 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

Stability improvement of MAPbI3-based perovskite solar cells using a photoactive solid-solid phase change material

Funding Information: The authors would like to acknowledge the financial support from the research department of Tarbiat Modares University (Research group of phase change materials, Grant No. IG-39710 and research group of nano plasma photonic, IG-39704 ). Maryam Mousavi would acknowledge the financial support from Fortum and Nestse Foundation (Grant No. 20210045 ), Espoo, Finland. Publisher Copyright: © 2021In this work, to increase the optical and thermal stability of perovskite solar cells, the composition of the perovskite layer is engineered by adding azobenzene (AZO) as a photoswitchable organic molecule. In this regard, solar cells with the FTO/b-TiO2/m-TiO2/CH3NH3PbI3/HTM/Au structure are fabricated using spiro-OMETAD hole transporting layer. Remarkably, an improvement of the optical, thermal, and structural stability of the devices comprising 5%, 10%, and 20% AZO is observed. Through the solid-solid phase-change mechanism of AZO, harmful UV radiation is absorbed and leads to photoisomerization between the trans and cis isomers, thus aiding in the management of thermal stresses on the device. Devices with pure perovskite absorber layer and perovskite absorber layer containing 10 wt% AZO retained 43% and 70% of their initial performances, respectively, after 70 min of exposure to sunlight. Furthermore, after 1440 h of storage in ambient conditions (25 ℃ and 42% relative humidity), the reference device maintains 35% of its initial performance while the device containing 10 wt% AZO retains 89% of its initial performance. In the case of thermal stability, the device containing 10% AZO shows superior thermal stability by keeping about 55% of its initial efficiency after exposure to a temperature of 85 ℃ and one sun illumination, simultaneously, for 60 min, compared to the reference device which retains only 35% of its performance under the same condition.Peer reviewe