Efficient, Flexible, and Ultra‐Lightweight Inverted PbS Quantum Dots Solar Cells on All‐CVD‐Growth of Parylene/Graphene/oCVD PEDOT Substrate with High Power‐per‐Weight

Abstract Ultra‐lightweight and flexible solar cells are desired for many potential applications, such as self‐powered aviation, wearable electronics, and the Internet of things. PbS quantum dots (QDs) are good candidates for this purpose due to their low‐cost and low‐temperature processing. In this work, a thin layer of parylene (1 µm) is deposited on a poly(ethylene teraphthalate) (PET) substrate using chemical vapor deposition (CVD) and is employed as a flexible substrate for PbS QDs solar cell. Here, the commonly used ITO electrode in the QDs photovoltaics (PVs) is replaced by CVD‐graphene and its wettability issue is addressed using a thin layer of oxidative CVD poly(3,4‐ethylene dioxythiophene) (oCVD PEDOT), which also works as second hole transporting layer in the device. Inverted PbS QDs device is fabricated on PET/parylene/graphene/oCVD PEDOT stack and finally by removing the PET substrate, an ultra‐lightweight PbS QDs solar cell is achieved. Using this architecture, a power conversion efficiency (PCE) of 7.1% and a power‐per‐weight of 12.3 W g −1 are achieved. Additionally, the QDs device on graphene shows good flexibility as compared to the device on PET/ITO. This work highlights the advantages of oCVD PEDOT and CVD‐graphene for the fabrication of flexible and ultralight weight photostatics.