In two new single n+(p+)−p(n) X(x)-alloy junction solar cells at 300 K, [X(x)≡CdSe1−xSx, CdSe1−xTex], 0≤x≤1, by basing on the same physical model-and-treatment method, as used in our recent works [1, 2], and also other works [3-6], some important results, obtained in the present work, are reported in the following.As noted in Tables 2.1, 3.1, 4.1 and 5.1, the dark carrier-minority saturation current density JoI(oII) decreases slightly with increasing rd(a)-radius for given x, and decreases strongly with increasing x, for given rd(a)-radius. Further, as discussed in Eq. (45), at a same Voc, both JoI(oII) and nI(II) have the same variations for same physical conditions.In particular, at x=0 and for Sn+Cd(Cd+Sn), both n+(p+)-p(n) CdSe1-xSx(Tex)[≡CdSe ] alloys become CdSe-crystals, as observed in Tables 1.1 and 1.2, and therefore, as given in Tables 2.2 (3.2), and 4.2 (5.2), we get the same numerical results of nImax.(IImax.)[=28.184 % (28.310 %)].Further, at x=1 and for Sn+Cd(Cd+Sn), we obtain: (a) in the n+(p+)-p(n) CdSe1-xSx(Tex)[≡CdS ] alloy-junction solar cells, nImax.(IImax.)=34.375 % (33.72 %) and TH=457.1 K (452.6 K), as those given in Tables 2.2 (3.2), and (b) in the +(p+)-p(n) CdSe1-xTex(Tex)[≡CdTe ] alloy-junction solar cells, nImax.(IImax.)=25.676 % (25.443 %), according to: TH=403.6 K (402.4 K), respectively, as those given in Tables 4.2 (5.2).Finally, from above remarks, we could conclude that, in order to obtain the highest efficiencies, the present (CdSe1-xSx, CdSe1-xTex)- crystalline alloy junction solar cells could be chosen rather than the crystalline (CdSe, CdTe)-junction solar cells [1, 2], yielding the highest efficiencies equal to: 26.55 % and 23.69 %, respectively.