Enhancing the Absorbance and Carrier Extraction of Lead Sulfide Quantum Dot Solar Cells by the Bilayer ZnO with a Self-Assembly Optical Structure

Enhancing the absorption of incident light and promoting the effective separation of carriers are two effective strategies to improve the power conversion efficiency of lead sulfide quantum dots (PbS CQDs) solar cells. Herein, a simple solution spin-coating method to synthesize a novel ZnO electron transport layer with a wrinkled surface structure is developed. ZnO-wrinkled surface structure can enhance the absorption of PbS CQDs solar cells in the range of 600–1000 nm compared with the normal planar ZnO film, leading to the enhancement in the short-current density. Further, by combining the wrinkled and planar ZnO to form a bilayer ZnO, the energy band alignment between ZnO and PbS CQDs is more suitable for the carrier transmission. Finally, PbS CQDs solar cell based on the bilayer ZnO yields a champion efficiency of up to 13.5%, presenting almost 10% enhancement compared to that based on the single planner ZnO. This method provides a simple and cost-effective method to enhance the efficiency of PbS CQDs thin-film solar cells.