Tunable Transparent Conductors Based on SnO2: Theoretical and Experimental Studies of Codoping.

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Transparent conducting oxides (TCOs) are widely used in modern electronics because they have both high transmittance and good conductivity, which is beneficial for many applications such as light-emitting diodes. Tailoring electronic states and hence the conductive types by design is important for developing new materials with optimal properties for TCOs. SnO2, with a wide band gap, low cost, no toxins, and high stability, is a promising host material for TCOs. Here, we performed a set of hybrid-exchange density functional theory calculations on the two-element and three-element codoped SnO2 by using Sr, Ta, Al, Ga, V, and Nb, which were then validated by the relevant experimental works on SnO2. As predicted by the first-principles calculations, the controllability of the electronic states to be n- or p-type can be demonstrated experimentally by varying the relative doping concentration between donors (Ta/Nb) and acceptors (Al/Ga). One of the main advantages for these codoping methods is that the charge neutrality problem caused by the dopant can be circumvented. The thin films fabricated showed a low sheet resistance (down to ∼450 Ω/□) and a high optical transparency (above 80%). The combination of our calculations and experimental material fabrication and characterizations has shown a great potential for codoping SnO2 for (i) the efficient processing of the integrated circuit composed of both p-type and n-type transistors (using the same target precursors during the deposition) and (ii) a good lattice matching for p-n junctions. Most importantly, our calculations, supported by the experimental works, point to a promising route to accelerate the discovery process for the alternative cost-effective and high-performance indium-free TCOs using computational material design.