Table 7.

Structural and optical data of thallium and gold halide perovskites

Perovskite	Sim./exp.	Crystal system (space group)	Dimensionality	Band gap/eV	References
CsTlF3 $({\text{CsTl}}_{0.5}^{+}{\text{Tl}}_{0.5}^{3+}{\text{F}}_3)$	Exp.	Cubic ($Fm\overline{3}$ m)	3D	–	[58, 59]
CsTlCl3 $({\text{CsTl}}_{0.5}^{+}{\text{Tl}}_{0.5}^{3+}{\text{F}}_3{\text{Cl}}_3)$	Exp.	Tetragonal (I4/m) Cubic (Fm $\overline{3}$ m)	3D	ca. 2.5	[58, 59]
CH3NH3Tl0.5Bi0.5I3	Sim.	Tetragonal	–	1.68	[151]
Cs2AuIAuIIICl6	Exp.	Tetragonal (I4/mmm)	3D	2.04	[60, 152]
Cs2AuIAuIIIBr6	Exp.	Tetragonal (I4/mmm)	3D	1.60	[152, 153]
Cs2AuIAuIIII6	Exp.	Tetragonal (I4/mmm)	3D	1.31	[61, 152, 153]
[NH3(CH2)7NH3]2[(AuII2)(AuIIII4)(I3)2]	Exp.	Triclinic (P $\overline{1}$)	2D	0.95	[62]
[NH3(CH2)8NH3]2[(AuII2)(AuIIII4)(I3)2]	Exp.	Monoclinic (C2/m)	2D	1.14	[62]

These materials have not been implemented in photovoltaic devices so far