Abstract
AbstractHalide perovskite semiconductors have risen to prominence in photovoltaics and light‐emitting diodes (LEDs), but traditional oxide perovskites, which overcome the stability limitations of their halide counterparts, have also recently witnessed a rise in potential as solar absorbers. One of the many important factors underpinning these developments is an understanding of the role of dimensionality on the optoelectronic properties and, consequently, on the performance of the materials in photovoltaics and LEDs. This review article examines the role of structural and electronic dimensionality, as well as form factor, in oxide and halide perovskites, and in lead‐free alternatives to halide perovskites. Insights into how dimensionality influences the band gap, stability, charge‐carrier transport, recombination processes and defect tolerance of the materials, and the impact these parameters have on device performance are brought forward. Particular emphasis is placed on carrier/exciton‐phonon coupling, which plays a significant role in the materials considered, owing to their soft lattices and composition of heavy elements, and becomes more prominent as dimensionality is reduced. It is finished with a discussion of the implications on the classes of materials future efforts should focus on, as well as the key questions that need to be addressed.
Highlights
Halide perovskite semiconductors have risen to prominence in photovoltaics and light-emitting diodes (LEDs), but traditional oxide perovskites, which overcome the stability limitations of their halide counterparts, have recently witnessed a rise in potential as solar absorbers
Inorganic oxide perovskites are the classical perovskites since their first discovery as a mineral in nature, they have only recently demonstrated promise for photovoltaics, with 8.1% power conversion efficiency achieved in the double perovskite Bi2FeCrO6
Owing to the multiferroic nature of oxide perovskites, there is the opportunity to explore novel concepts, such as the ferroelectric photovoltaic effect, which can enable open-circuit voltages exceeding the band gap
Summary
While lead-halide perovskites are studied by hundreds of groups worldwide, inorganic perovskites based on oxides, sulfides, and selenides are being studied for their optoelectronic properties by a smaller, but growing, community. The ideal band gap for a single band gap solar cell is 1.34 eV according to the detailed balance limit.[42] For twoterminal tandem solar cells with a c-Si bottom cell, the ideal top cell bandgap is approximately 1.72 eV.[43] Wider band gaps are more suitable for water splitting, but even in this case, the optimal band gap of 2.03 eV is below the band gap of typical single oxide perovskites.[44] Titanates such as PbTiO3 (PTO) and BaTiO3 (BTO) are well known for their ferroelectric properties. Ru-doping enabled the band gap of SrTiO3 to be reduced from 3.2 to 2.0 eV.[54]
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