Lead-free perovskite solar cells enabled by hetero-valent substitutes

Abstract

<p>In this perspective, we present strategies that foster the expulsion of lead from perovskites to obtain a non-hazardous active material.</p>

Lead-Free Metal Halide Perovskites for Hydrogen Evolution from Aqueous Solutions

“…Beyond the earlier mentioned MHPs, double ones have been also reported in literature [57,60,61]. They can have the general formula A 2 B'B"X 6 in which A is a monovalent cation, B' and B" are a pair of heterovalent (i.e., monovalent and trivalent) metal cations to give an average +2 valence state (e.g., Ag + and Bi 3+ ), while X is a halide [60][61][62].…”

Charge Transport Properties of Methylammonium Lead Trihalide Hybrid Perovskite Bulk Single Crystals

“…[ 32 ] Finally, looking to the future there is a wide variety of frontier research currently being undertaken regarding hybrid perovskites ranging from attempting to further increase the stability of the material, such as by replacing the B 2+ cation for heterovalent cation or a double perovskite crystal structure to improve the charge transport properties without compromising on stability and the unwanted use of Lead. [ 30,34 ] Further examples of this are shown, through the insertion of carbon nanotubes into the crystals, where it is possible to learn more about the large light absorption coefficient, intrinsic low conductivity, and other properties that will affect the device structure, or furthering environmental efforts to remove dangerous chemicals such as GBL from the process completely using less harmful solvents in the synthesis stage as PC. [ 48,145 ] So for the whole, if current research trends into hybrid perovskites continues to accelerate it is likely we will see the single‐crystal hybrid perovskites in a range of technological applications, within the next decade.…”

“…[ 30–33 ] Other attempts at creating lead free hybrid perovskites have looked at replacing the lead cation with a heterovalent cation, which subsequently will change the crystal structure of the hybrid perovskite. [ 34 ] In these scenarios either the divalent Pb 2+ is replaced with a monovalent cation like Ag + , Na + , and a trivalent cation such as Sb 3+ , Bi 3+ , or Pb 2+ is replaced only by a trivalent cation or only a tetravalent cation for example Te 4+ , Ti 4+ , and a vacancy. [ 34,35 ] In the first case, the crystal structure changes to A 2 B + B 3+ X 6 and is now a double perovskite; in the second case, the new crystal structure is A 3 B 2 X 9 ; and in the third, it is also a case of a double perovskite with a crystal structure of AB 4+ X 6 .…”

“…[ 34 ] In these scenarios either the divalent Pb 2+ is replaced with a monovalent cation like Ag + , Na + , and a trivalent cation such as Sb 3+ , Bi 3+ , or Pb 2+ is replaced only by a trivalent cation or only a tetravalent cation for example Te 4+ , Ti 4+ , and a vacancy. [ 34,35 ] In the first case, the crystal structure changes to A 2 B + B 3+ X 6 and is now a double perovskite; in the second case, the new crystal structure is A 3 B 2 X 9 ; and in the third, it is also a case of a double perovskite with a crystal structure of AB 4+ X 6 . [ 34 ] In these three cases, the PCE in solar cells are still poor in comparison to the methylammonium lead trihalide, however, one with the most potential based on cesium is Cs 2 AgBiBr 6 which in single crystal form contains a photoluminescence lifetime of 660 ns, an indirect bandgap of 1.95 eV, 11.81 cm 2 V −1 s −1 mobility, from the space‐charge‐limited current (SCLC) method and is found to be thermal and moistly stable.…”

“…[ 34 ] In these three cases, the PCE in solar cells are still poor in comparison to the methylammonium lead trihalide, however, one with the most potential based on cesium is Cs 2 AgBiBr 6 which in single crystal form contains a photoluminescence lifetime of 660 ns, an indirect bandgap of 1.95 eV, 11.81 cm 2 V −1 s −1 mobility, from the space‐charge‐limited current (SCLC) method and is found to be thermal and moistly stable. [ 34,36–38 ]…”