The empirical relation of
between the transition temperature of optimum doped superconductors T
co and the mean cationic charge
, a physical paradox, can be recast to strongly support fractal theories of high-T
c superconductors, thereby applying the finding that the optimum hole concentration of σ
o = 0.229 can be linked with the universal fractal constant δ
1 = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ
1, exemplified through the energy gap relation k
BT
c ≈ 5Δ
0/δ
1, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T
c superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of
less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1
﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.