A composition formed of a mixture of a first compound and a second compound wherein the first compound has a different chemical structure than the second compound. The first compound and the second compound are both organic compounds. At least one of the first compound and the second compound contains at least one less abundant stable isotope atom. The first compound has an evaporation temperature T1 and the second compound has an evaporation temperature T2 where both T1 and T2 are between 100 to 400 ° C. and the absolute value of T1-T2 is less than 20 ° C. The first compound has a concentration C1 in said mixture and a concentration C2 in a film formed by evaporating said mixture in a high vacuum deposition tool with a chamber base pressure between 1×10−6 Torr to 1×10−9 Torr, at a 2Å/sec deposition rate on a surface positioned at a predefined distance away from the mixture being evaporated; and wherein absolute value of (C1-C2)/C1 is less than 5%.
一种由第一种化合物和第二种化合物混合物组成的组合物,其中第一种化合物的
化学结构与第二种化合物不同。第一种化合物和第二种化合物都是有机化合物。第一种化合物和第二种化合物中至少有一种含有至少一种含量较少的稳定同位素原子。第一种化合物的蒸发温度为 T1,第二种化合物的蒸发温度为 T2,其中 T1 和 T2 均在 100 至 400 ° C 之间,且 T1-T2 的绝对值小于 20 ° C。第一种化合物在所述混合物中的浓度为 C1,在通过高真空沉积工具蒸发所述混合物而形成的薄膜中的浓度为 C2,该工具的腔体基础压力在 1×10-6 托至 1×10-9 托之间,以 2Å/sec 的沉积速率沉积在与被蒸发混合物保持预定距离的表面上;其中 (C1-C2)/C1 的绝对值小于 5%。