Cascade surface modification of colloidal quantum dot inks enables efficient bulk homojunction photovoltaics

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Precise control over carrier type and doping in semiconductor materials is crucial for advanced optoelectronic devices.
• Surface chemistry modification in colloidal quantum dots (CQDs) allows property tuning but often compromises passivation and solubility, hindering complex architectures like homojunctions.

Purpose of the Study:

• To introduce a novel cascade surface modification scheme for CQDs.
• To achieve simultaneous control over doping, solubility, and surface passivation in CQDs.
• To enable the fabrication of CQD bulk homojunction solids for enhanced performance.

Main Methods:

• A cascade surface modification strategy was employed on CQDs.
• Development of n-type and p-type CQD inks with full miscibility and complete surface passivation.
• Fabrication of homogeneous CQD bulk homojunction films.

Main Results:

• The new scheme provides independent control over doping and solubility.
• Achieved fully miscible n-type and p-type CQD inks in a single solvent.
• Fabricated homogeneous CQD bulk homojunction films with a 1.5-fold increase in carrier diffusion length.
• Demonstrated a record power conversion efficiency of 13.3% for CQD solar cells.

Conclusions:

• The cascade surface modification overcomes previous limitations in CQD tuning.
• This advancement facilitates the creation of advanced CQD architectures, specifically bulk homojunctions.
• The developed inks and films pave the way for highly efficient colloidal quantum dot solar cells.