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

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 mu m) 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.