Dopant Control of Solution-Processed CuI:S for Highly Conductive p-Type Transparent Electrode.

ABSTRACT

Copper iodide (CuI) has garnered considerable attention as a promising alternative to p-type transparent conducting oxides owing to its low cation vacancy formation energy, shallow acceptor level, and readily modifiable conductivity via doping. Although sulfur (S) doping through liquid iodination has exhibited high efficacy in enhancing the conductivity with record high figure of merit (FOM) of 630 00 MΩ-1, solution-processed S-doped CuI (CuIS) for low-cost large area fabrication has yet to be explored. Here, a highly conducting CuIS thin-film for p-type transparent conducting electrode (TCE) is reported using low temperature solution-processing with thiourea derivatives. The optimization of thiourea dopant is determined through a comprehensive acid-base study, considering the effects of steric hindrance. The modification of active groups of thioureas facilitated a varying carrier concentration range of 9 × 1018-2.52 × 1020 cm-3 and conductivities of 4.4-390.7 S cm-1. Consequently, N-ethylthiourea-doped CuIS exhibited a FOM value of 7 600 MΩ-1, which is the highest value among solution-processed p-type TCEs to date. Moreover, the formulation of CuIS solution for highly conductive p-type TCEs can be extended to CuIS inks, facilitating high-throughput solution-processes such as inkjet printing and spray coating.