The present study reveals the ferroelectric nature of the novel (Sr 2 Ta 2 O 7 ) 100-x (La 2 Ti 2 O 7 ) x layered perovskite materials and highlights a large variation of their permittivity under electric fields associated with very low dielectric loss in the radio-frequency range. More precisely, an ideal solid solution has been evidenced within the composition range 0 ≤ x ≤ 5 with lattice parameters and cell volume varying linearly with x. The relative permittivity also depends on the composition and reaches a maximum value (365 @10kHz, RT), associated with a high tunability (17.6 % @0.38 kV/mm) with very low dielectric loss lower than 2.10 -3 . Variation of the relative permittivity as a function of the temperature is also demonstrated, with the existence of a temperature maximum, increasing with the composition. Polarization-electric field (P-E) measurements feature hysteresis loops for compositions x ≥ 1.85, in conjunction with current peaks in the I-E curves originating from ferroelectric domains switching.Keywords : perovskiteferroelectrictunability -Sr 2 Ta 2 O 7 -La 2 Ti 2 O 7

Flexible thin film solar cells represent the future. This study concentrates on making CuInSe2 based solar cells non rigid by depositing the rear molybdenum contact onto inox 316.

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