Tremendous work has been made recently to improve the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs); the best reported value is now over 23%. However, further improving the PCEs of PSCs is challenged by material properties, device stability, and packaging technologies. Here, we report a new approach to increase the PCEs of flexible PSCs via introducing the piezo-phototronic effect in the PSCs by growing an array of ZnO nanowires on flexible plastic substrates, which act as the electron-transport layer for PSCs. From the piezo-phototronic effect, the absolute PCE was improved from 9.3 to 12.8% for flexible perovskite solar cells under a static mechanical strain of 1.88%, with a ∼40% enhancement but no change in the components of materials and device structure. A corresponding working model was proposed to elucidate the strategy to boost the performance of the PSCs. These findings present a general approach to improve PCEs of flexible PSCs without changing their fundamental materials.
Keywords: ZnO nanowires; perovskite solar cells; piezo-phototronic effect; power conversion efficiency; strain modulated.