Extremely lightweight and ultra-flexible infrared light-converting quantum dot solar cells with high power-per-weight output using a solution-processed bending durable silver nanowire-based electrodeElectronic supplementary information (ESI) available. See DOI: 10.1039/c7ee02772a

Lightweight and flexible solar cells are highly interesting materials for use in new applications, such as spacecraft, aircraft and personal pack load. PbS colloidal quantum dots (CQDs) exhibit a broad and strong light absorption spectrum covering the ultraviolet-visible-near infrared region, allowing for incorporation of very thin CQD films into solar cells with high power conversion efficiency (PCE) from solar light to electricity. Herein, we report an extremely lightweight and ultra-flexible CQD solar cell constructed on a polyethylene naphthalate substrate with a thickness of 1.3 μm. A solution-processed Ag nanowire network with excellent mechanical, optical and electrical properties was prepared as the front-electrode in the solar cell. The thickness of the complete CQD solar cell is less than 2 μm, and ∼10% PCE with a weight of 6.5 g m −2 is achieved, resulting in a power-per-weight output of 15.2 W g −1 . The flexible solar cell possesses durable mechanical properties and maintains high-level photovoltaic performance under extreme deformation and after repeated compression-stretching deformation. Moreover, the flexible CQD solar cell shows impressive stability both under continuous illumination and after storage under ambient conditions. These results reveal that solution-processed CQDs are compatible with an ultra-flexible substrate for the construction of ultra-lightweight infrared light-converting CQD solar cells with possibilities for new exciting solar energy applications. Lightweight and flexible solar cells are highly interesting materials for use in new applications, such as spacecraft, aircraft and personal pack load.