Ternary PbSeS quantum dots with 3.8× higher electron mobility enable thicker absorber layers and improved power conversion efficiency in colloidal quantum dot solar cells.
Abstract
Colloidal quantum dot (CQD) solar cells based on conventional PbS quantum dots face a fundamental limitation: short carrier diffusion lengths arising from inter-dot hopping transport prevent the use of thick absorber layers needed for complete light harvesting and restrict power conversion efficiency. In this work, we engineer ternary PbSeS quantum dots that maintain a near-optimal single-junction bandgap while significantly enhancing charge transport through controlled selenium incorporation. Through tailored anion precursor chemistry, uniform alloying is achieved while maintaining absorption peaks near 930 nm, close to the Shockley–Queisser optimal bandgap. Space-charge-limited current analysis reveals 3.8× and 2.3× improvements in electron and hole mobility compared to PbS quantum dots, respectively. These mobility gains reduce carrier recombination in fully depleted architectures, and PbSeS devices maintain high efficiency with absorber layers up to ~500 nm, whereas conventional PbS cells degrade with increased thickness. This work establishes ternary PbSeS quantum dots as a promising platform for overcoming diffusion length limitations in quantum dot photovoltaics. [Link to Journal website (Inorganic Chemistry Frontiers, RSC)]
Congratulations, Yongwoo!