Fabrication of efficient PbS colloidal quantum dot solar cell with low temperature sputter-deposited ZnO electron transport layer

Preparation of electron transport layer (ETL) with high uniformity by convenient and low-temperature process is of essential importance for the future development of colloidal quantum dot solar cells (CQDSCs) into large-area and flexible devices. Herein we utilized magnetron sputtering technique to deposit ZnO thin film as the ETL of PbS CQDSCs. The ZnO film deposited at ambient temperature displayed preferential growth along (001) direction, pinhole free morphology, and good optical transmittance. On rigid SnO2:F (FTO) conductive glass substrates, PbS CQDSCs with sputtered ZnO ETL achieved a power conversion efficiency of 6.47% under AM 1.5 G simulated solar irradiation, which was higher than the 6.02% efficiency of the CQDSC fabricated on the benchmarked ZnO nanocrystals ETL. The good uniformity of sputtered ZnO film also facilitated the consistency of photovoltaic parameters of big-sized CQDSCs, as demonstrated by the similar output of four series-connected CQDSC units fabricated in one batch with a total active area of 14.4 cm2. Flexible PbS CQDSCs was also fabricated on the sputtered ZnO ETL, using In2O3:Sn-coated polyethylene terephthalate (ITO-PET) as the substrate, which achieved a power conversion efficiency of 3.87% and displayed negligible decline of the photovoltaic parameters after 100-time bending treatment. Our research demonstrates that the magnetron-sputtered ZnO film, with favorable features of low-temperature process, large-area continuity, and high bending tolerance, presents promising potential for the future development of PbS CQDSCs.