Developments on Perovskite Solar Cells (PSCs): A Critical Review

This review provides detailed information on perovskite solar cell device background and monitors stepwise scientific efforts applied to improve device performance with time. The work reviews previous studies and the latest developments in the perovskite crystal structure, electronic structure, device architecture, fabrication methods, and challenges. Advantages, such as easy bandgap tunability, low charge recombination rates, and low fabrication cost, are among the topics discussed. Some of the most important elements highlighted in this review are concerns regarding commercialization and prototyping. Perovskite solar cells are generally still lab-based devices suffering from drawbacks such as device intrinsic and extrinsic instabilities and rising environmental concerns due to the use of the toxic inorganic lead (Pb) element in the perovskite (ABX3) light-active material. Some interesting recommendations and possible future perspectives are well articulated.

Influence of metal halide perovskite modifications on structure and functionality

<p>Metal halide perovskites (ABX₃) represent an important class of materials with respect to optoelectronic applications such as photovoltaic and light-emitting devices. In this thesis, modification of these materials was explored through metal substitutions, halide substitutions and also nanocrystal synthesis. The ability for these modifications to take place was analyzed, and related to the effects on structural and optoelectronic properties. Heterovalent metal substitutions were explored through the substitution of Bi³⁺ into methylammonium lead iodide (MAPbI₃). It was found that a two phase material composed of MAPbI₃ and MA₃Bi₂I₉ forms during these substitutions. This resulted in changes to electron-hole generation in the thin films and separation in photovoltaic devices, as observed through optical absorption and current-voltage measurements. Substitutions of Bi³⁺ and Tl⁺ were also carried out at dopant concentrations of 0.1–1%. Although the bulk crystal structure was maintained here, the power conversion efficiencies of devices decreased, with a bigger effect measured for Bi³⁺ doping. The ability for halide ions in MAPbBr₃ to be substituted with the thiocyanate ion (SCN)⁻ was investigated and compared to previous reports concerning MAPbI₃. From the studies conducted here, it is unlikely that the (SCN)⁻ ion becomes incorporated into the perovskite crystal lattice. This appeared to be primarily due to the reactivity of MA⁺ ion with (SCN)⁻. Finally, Cs₃Bi₂I₉ nanocrystals were synthesized via the hot injection method. This was supported through XRD, TEM and EDS measurements, where the crystals were found to display hexagonal symmetry. Subsequent experiments on the mixed halide nanocrystals (I/Br) revealed the sensitive nature of this synthesis to oxygen contamination.</p>

Influence of metal halide perovskite modifications on structure and functionality

<p>Metal halide perovskites (ABX₃) represent an important class of materials with respect to optoelectronic applications such as photovoltaic and light-emitting devices. In this thesis, modification of these materials was explored through metal substitutions, halide substitutions and also nanocrystal synthesis. The ability for these modifications to take place was analyzed, and related to the effects on structural and optoelectronic properties. Heterovalent metal substitutions were explored through the substitution of Bi³⁺ into methylammonium lead iodide (MAPbI₃). It was found that a two phase material composed of MAPbI₃ and MA₃Bi₂I₉ forms during these substitutions. This resulted in changes to electron-hole generation in the thin films and separation in photovoltaic devices, as observed through optical absorption and current-voltage measurements. Substitutions of Bi³⁺ and Tl⁺ were also carried out at dopant concentrations of 0.1–1%. Although the bulk crystal structure was maintained here, the power conversion efficiencies of devices decreased, with a bigger effect measured for Bi³⁺ doping. The ability for halide ions in MAPbBr₃ to be substituted with the thiocyanate ion (SCN)⁻ was investigated and compared to previous reports concerning MAPbI₃. From the studies conducted here, it is unlikely that the (SCN)⁻ ion becomes incorporated into the perovskite crystal lattice. This appeared to be primarily due to the reactivity of MA⁺ ion with (SCN)⁻. Finally, Cs₃Bi₂I₉ nanocrystals were synthesized via the hot injection method. This was supported through XRD, TEM and EDS measurements, where the crystals were found to display hexagonal symmetry. Subsequent experiments on the mixed halide nanocrystals (I/Br) revealed the sensitive nature of this synthesis to oxygen contamination.</p>