Enhancing PbS Colloidal Quantum Dot Tandem Solar Cell Performance by Graded Band Alignment

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Colloidal quantum dot (CQD) solids offer tunable bandgaps, making them promising for tandem solar cells.
• Quantum dot tandem solar cell development lags behind single-junction cells due to limited diffusion length.
• Short diffusion lengths restrict absorber layer thickness, hindering power conversion efficiency (PCE).

Purpose of the Study:

• To fabricate a high-efficiency, two-terminal, monolithic, solution-processed quantum dot tandem solar cell.
• To overcome the limitations imposed by short diffusion lengths in CQD solar cells.
• To demonstrate a general strategy for enhancing the efficiency of thin-film tandem solar cells.

Main Methods:

• Optical modeling guided the design process.
• A graded band alignment strategy was employed.
• Judicious selection of nanoparticle surface chemistry and quantum dot size was used to tune work functions and band alignment.

Main Results:

• A two-terminal monolithic solution-processed quantum dot tandem solar cell was successfully fabricated.
• A power conversion efficiency (PCE) of 6.8% was achieved.
• The band grading approach effectively utilized complementary tuning of work functions and band alignment.

Conclusions:

• The developed graded band alignment strategy is a viable method for improving CQD tandem solar cell efficiency.
• This research presents a generalizable approach for enhancing PCE in thin-film tandem solar cells.
• The findings contribute to the advancement of colloidal quantum dot solar cell technology.