Core/shell PbSe/PbS QDs TiO₂ heterojunction solar cell

Quasi type-II PbSe/PbS quantum dots (QDs) are employed in a solid state high efficiency QD/TiO₂ heterojunction solar cell. The QDs are deposited using layer-by-layer deposition on a half-micrometer-thick anatase TiO₂ nanosheet film with (001) exposed facets. Theoretical calculations show that the carriers in PbSe/PbS quasi type-II QDs are delocalized over the entire core/shell structure, which results in better QD film conductivity compared to PbSe QDs. Moreover, PbS shell permits better stability and facile electron injection from the QDs to the TiO₂ nanosheets. To complete the electrical circuit of the solar cell, a Au film is evaporated as a back contact on top of the QDs. This PbSe/PbS QD/TiO₂ heterojunction solar cell produces a light to electric power conversion efficiency (η) of 4% with short circuit photocurrent (J_sc) of 17.3 mA/cm². This report demonstrates highly efficient core/shell near infrared QDs in a QD/TiO₂ heterojunction solar cell.