Methodologies in Search of p-type Transparent Conductors

摘要

P-type transparent conductors are rare in nature but could lead to a lot technological innovations. A systematic search for p-type transparent conductors can be divided into two types: to search for (I) experimentally unknown compounds and (II) experimentally known ones. The difference between the two types of search lies in the fact that we always start with the experimental crystal structure in type II search while such information is lacking in the type I search. To make the type I research possible, a reasonably efficient method in predicting the ground state crystal structure is required. And the evolutionary algorithm with the real-space cut-and-splice method is a promising candidate for the task.;For both type I and type II searches, we have to accurately predict the fundamental band gap and the hole conductivity. Corrections to density functional theory band gap, such as screened exchange LDA (sxLDA) or G0W0 , are required. The hole conductivity is linearly dependent on the hole concentration and inversely proportional to the hole effective mass. And we focused on the study of host material properties, the fundamental band gaps and hole effective masses, in the oxide sulfide family and eight promising candidates as p-type transparent conducting hosts were found.;The hole population in the known transparent conducting oxides (TCOs) is mostly orig- inating from intrinsic point defects. However, a material La5Cu6O4S7 , whose hole conduc- tivity is an order of magnitude higher than the known TCOs, has its holes originating from a line structure, namely the breaking of dimers on the sulfur chain. The sulfur chain is optically inactive and serves purely to generate holes traveling in the Cu6S6 layers at finite temperature. This interesting hole-generating mechanism could open up new possibilities to achieve high hole conductivity in p-type TCs.