Removal of residual compositions by powder engineering for high efficiency formamidinium-based perovskite solar cells with operation lifetime over 2000 h

Defects as a result of structural imperfections and/or extrinsic impurities in the perovskite films have a detrimental effect on efficiency and stability of perovskite solar cells (PSCs). Here, we propose to use pre-synthesized crystalline perovskite with perfect stoichiometry to control and lower the density of defects from precursors by the powder engineering method. Compared with raw materials (i.e., PbI2 and FAI) based perovskites, the average efficiency of the PSCs fabricated based on these pre-synthesized perovskite precursors increased from 18.62% to 19.85%. Moreover, the unwanted intermediate chemical compositions (i.e., the unreacted phases and residual solvent) in the raw material-based perovskite films were significantly reduced in the pre-synthesized delta-FAPbI3 and alpha-FAPbI3 perovskites according to the secondary ion mass spectroscopy depth profiling results. Finally, we obtained the champion efficiency of 22.76% for alpha-FAPbI3 and 23.05% for FAPb(I0.9Br0.1)3 based PSCs. Long-term operational stability measurements of the encapsulated FAPb(I0.9Br0.1)3 based PSCs showed a slow decay and maintained the efficiency about 88% after 1200 h (T80 > 2000 h). Furthermore, a proof-of-concept integrated perovskite solar module-lithium ion battery-light-emitting diode device was demonstrated.

Automated summary

Using pre-synthesized crystalline perovskite with perfect stoichiometry can control and reduce the density of defects in perovskite solar cells, resulting in an increase in efficiency. Pre-synthesized perovskite precursors showed a significant reduction in unwanted intermediate chemical compositions, leading to higher efficiencies in PSCs. Long-term stability measurements also demonstrated the effectiveness of using pre-synthesized perovskite in improving the performance of PSCs.