The tunable bandgap of colloidal quantum dots (CQDs) makes them an attractive material for photovoltaics (PV). The best present-day CQD PV devices employ zinc oxide (ZnO) as an electron transport layer; however, it is found herein that ZnO's surface defect sites and unfavorable electrical band alignment prevent devices from realizing their full potential. Here, chloride (Cl)-passivated ZnO generated from a solution of presynthesized ZnO nanoparticles treated using an organic-solvent-soluble Cl salt is reported. These new ZnO electrodes exhibit decreased surface trap densities and a favorable electronic band alignment, improving charge extraction from the CQD layer and achieving the best-cell power conversion efficiency (PCE) of 11.6% and an average PCE of 11.4 ± 0.2%.
- band alignment
- quantum-dot solar cells