13:15 〜 13:30
▲ [15p-A34-2] Bandgap engineering for enhancing photovoltaic properties of PbS quantum dot solar cells
キーワード：Colloidal quantum dots, Solar cell, Bandgap engineering
Colloidal quantum dots solar cells (CQDSCs) have recently reached promising power conversion efficiencies (η) of over 10%. However, CQD solids have relatively short minority carrier diffusion length (≤100nm), which limited the further improvement in the photovoltaic performance of CQDPV devices. Colloidal quantum dots offer broad tuning of semiconductor band-structure via the quantum size effect. Using a spatial energy band gradient engineering with quantum dots (QDs) of different sizes to enhance the minority carrier diffusion length of a photovoltaic device is a promising strategy for increasing the solar cell efficiency. In this study, we developed an air condition solution-processed TiO2/PbS quantum dot heterojunction solar cells, by applying a band alignment method to the active layer by means of 4 kinds of PbS QDs with different sizes. We found that the graded architecture solar cells exhibited a great increase (from 28 mA/cm2 to 34 mA/cm2) in short-circuit current density (Jsc), a high efficiency of 7.25% has been reached, as a result of the enhanced minority carrier lifetime and the improved charge transfer. Furthermore, the performance of unencapsulated devices remains unchanged for over 100 days of storage in air. Our results demonstrate that the band alignment of the active layer of CQDSCs is one effective method for improving the photovoltaic properties of CQDSCs.