Thin film solar cells based on the heterojunction of colloidal PbS quantum dots with CdS

Here we report on heterojunction PbS quantum dot (QD) solar cells using RF magnetron sputtered CdS as the n-type window layer. These solar cells generate large open circuit voltage compared to previously reported PbS-QD solar cells. Our investigations of this device design show an optimized CdS film thickness of 70 nm and an optimized PbS QD diameter of ∼2.7 nm, corresponding to a bandgap energy of ∼1.57 eV. Under simulated AM1.5 G illumination, we attain short circuit current as high as 12 mA-cm−2, an open circuit voltage of 0.65 V and efficiency as high as 3.3%.