2 CdP 2 has a smaller band gap (1.43 eV) compared to Ba 0.75 Sr 1.25 CdP 2 (1.81 eV). If one were to assume that a fraction of the band gap increase results in a shift of the conduction band minimum to higher energy, then a simple extrapolation of the V Cd formation energy (line with negative slope -2 in Figure ) could explain the decrease in DE n . Based on this observation, we formulate that the alloy compositions with lower Sr content (smaller x) are optimal for maximizing n-type dopability, as quantified by DE n . Taking the electronic and thermal transport, and dopability factors into consideration, we computationally predict that Ba 2(1 x) Sr 2x CdP 2 alloys with x = 0.35 0.70 are optimal, with lower x in that range preferred for larger dopability (DE n ).