A heterostructure p-n junction constituting of fluorite and perovskite semiconductors for electrochemical energy conversion.

[Display omitted] • The semiconductor heterostructure 5BKFC-5SNDC electrolyte was designed and developed using BKFC and SNDC. • 5BKFC-5SNDC electrolyte possessed good electrolyte function with high ionic conductivity. • The electron transmission was blocked and the ion transferring was promoted through p-n heterostructure in the electrolyte. • Fuel cell with 5BKFC-5SNDC electrolyte achieved high power density of 911 mWcm−2 at 550° C. A semiconductor heterostructure material based on p-type cubic perovskite Ba 0.9 K 0.1 Fe 0.5 Co 0.5 O 3-δ (BKFC) and n-type fluorite Sm 0.075 Nd 0.075 Ce 0.85 O 2-δ (SNDC) forms micro p-n junctions in the low-temperature solid oxide fuel cells (LT-SOFCs) improving the electrochemical performance. A highly power density of 911 mW·cm−2 at 550° C was obtained with this material combination as electrolyte in a fuel cell, which is 20 % higher than that of the LT-SOFCs with pure BKFC as electrolyte. An ionic conductivity of 0.14 S·cm−1 at 550° C was achieved when equal amounts of BKFC and SNDC were employed as the electrolyte. Profound analysis of the heterostructure p-n junction shows that it blocks electron transport through mixed electronic and ionic conductor and enhances ionic transport improving the electrochemical performance of the fuel cell. The BKFC-SNDC composite electrolyte materials is a potential electrolyte material for raising the power density of fuel cells at lower temperatures. [ABSTRACT FROM AUTHOR]