All-perovskite tandem solar cells hold the promise of surpassing the efficiency limits of single-junction solar cells1–3; however, until now, the best-performing all-perovskite tandem solar cells have exhibited lower certified efficiency than have single-junction perovskite solar cells4,5. A thick mixed Pb–Sn narrow-bandgap subcell is needed to achieve high photocurrent density in tandem solar cells6, yet this is challenging owing to the short carrier diffusion length within Pb–Sn perovskites. Here we develop ammonium-cation-passivated Pb–Sn perovskites with long diffusion lengths, enabling subcells that have an absorber thickness of approximately 1.2 μm. Molecular dynamics simulations indicate that widely used phenethylammonium cations are only partially adsorbed on the surface defective sites at perovskite crystallization temperatures. The passivator adsorption is predicted to be enhanced using 4-trifluoromethyl-phenylammonium (CF3-PA), which exhibits a stronger perovskite surface-passivator interaction than does phenethylammonium. By adding a small amount of CF3-PA into the precursor solution, we increase the carrier diffusion length within Pb–Sn perovskites twofold, to over 5 μm, and increase the efficiency of Pb–Sn perovskite solar cells to over 22%. We report a certified efficiency of 26.4% in all-perovskite tandem solar cells, which exceeds that of the best-performing single-junction perovskite solar cells. Encapsulated tandem devices retain more than 90% of their initial performance after 600 h of operation at the maximum power point under 1 Sun illumination in ambient conditions.
|Number of pages||6|
|State||Published - Mar 3 2022|
Bibliographical noteFunding Information:
Acknowledgements This work was financially supported by the National Key R&D Program of China (grant no. 2018YFB1500102), the National Natural Science Foundation of China (grant nos. 61974063 and 61921005), the Natural Science Foundation of Jiangsu Province (grant nos. BK20202008 and BK20190315), the Technology Innovation Fund of Nanjing University, Fundamental Research Funds for the Central Universities (grant nos. 0213/14380206 and 0205/14380252), the Frontiers Science Center for Critical Earth Material Cycling Fund (grant no. DLTD2109), the Program A for Outstanding PhD Candidate of Nanjing University, and the Program for Innovative Talents and Entrepreneur in Jiangsu. The work at the University of Toronto was supported by the US Department of the Navy, Office of Naval Research (grant no. N00014-20-1-2572). SciNet is funded by the Canada Foundation for Innovation under the auspices of Compute Canada. K.R.G., S.M.P. and H.R.A. acknowledge the US Department of Energy, Office of Basic Energy Sciences under grant no. DE-SC0018208 for supporting the photoelectron spectroscopy measurements.
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