Ultrafast Charge Transfer Dynamics and Charge Transport with Pyrediyne (PDY): Revealing the Role of a Novel Carbon-Based Electron Acceptor

Coupling of semiconductor quantum dots (QD) with carbon-based materials such as graphene, fullerene, carbon nanotube, and graphdiyne (GDY) has been proven to be an effective strategy to improve the performance of the photovoltaics due to the efficient charge extraction and enhanced charge transport of carbon-based materials. Analogous to GDY, recently, a new material known as pyrediyne (PDY) was reported from our group where pyrene rings are interconnected through a diacetylinic linkage. Although GDY has largely been explored in various fields including photovoltaics, battery, and superhydrophobicity, PDY has not been explored so far except for bioimaging application, largely because of the lack of understanding on the electronic behavior in the PDY interface. In this study, detailed charge transfer dynamics of CdTe QDs is investigated to understand the electronic process in the PDY interface in the presence of 0D PDY (PDYQD) and 2D PDY (PDYS) by using a combination of steady-state and time-resolved ultrafast spectroscopy measurements. The analysis provides an evidence for fast electron transfer from CdTe QDs to PDYQD. In addition, slow charge recombination of the transferred electron with the existing hole in CdTe QDs is evidenced as PDYS accepts the electron at a relatively slower rate. On the basis of the mechanistic investigation, an overall charge transfer scheme is proposed that accounts for the faster bleach recovery at an early time (picoseconds) and slower decay at a longer time (nanoseconds) scale. In addition, to ensure the applicability of PDY in real devices, four-probe photoconductivity measurements were employed, which shows improved photoconductivity (from sigma = 1.53 x 10(-6) to sigma = 5.10 x 10(-6) S m(-1)) for CdTe-PDYQD. These findings are very promising to advance both the design and the application scope of PDY in the field of clean energy research to enhance the device performances.

Automated summary

Coupling semiconductor quantum dots with carbon-based materials has been proven effective in improving the performance of photovoltaics. In this study, the charge transfer dynamics of CdTe quantum dots in the presence of PDY materials were investigated. The results showed fast electron transfer from CdTe quantum dots to PDYQD, while PDYS accepted the electron at a relatively slower rate. A comprehensive charge transfer scheme was proposed based on mechanistic investigation, and improved photoconductivity for CdTe-PDYQD was observed in four-probe photoconductivity measurements.