Electrodeposited and in situ carbon quantum dot embedded CdS thin films as electron transport layers

Cadmium sulfide (CdS) has been proposed as a promising alternative to zinc oxide (ZnO) electron transport materials, which are widely used in high-performance PbS solar cells but are known to suffer from poor stability and energy misalignment. However, the techniques currently used to grow CdS thin films allow limited control over characteristic properties such as thickness, morphology, and defect density. Herein, we demonstrate that electrodeposition technique can be an excellent method to deposit CdS, and when combined with in situ carbon quantum dot (CQD) embedding, denser films with improved surface uniformity, higher transparency and longer excited state lifetimes can be obtained. This technique, which is cost-effective and implantable on a large scale, allows simultaneous and precise control over thickness and charge carrier density, enabling us to achieve a remarkable efficiency of 7.47 % in CdS/PbS solar cells using an electrodeposited CdS for the first time. Thanks to faster exciton dissociation, interfacial charge transfer and charge carrier collection facilitated by the formation of type-II heterojunction between CQDs and CdS, the in situ embedding technique used in this study can be considered as a strategic approach to achieve higher cell performance in future.