RESUMEN
A stable perovskite heterojunction was constructed for inverted solar cells through surface sulfidation of lead (Pb)-rich perovskite films. The formed lead-sulfur (Pb-S) bonds upshifted the Fermi level at the perovskite interface and induced an extra back-surface field for electron extraction. The resulting inverted devices exhibited a power conversion efficiency (PCE) >24% with a high open-circuit voltage of 1.19 volts, corresponding to a low voltage loss of 0.36 volts. The strong Pb-S bonds could stabilize perovskite heterojunctions and strengthen underlying perovskite structures that have a similar crystal lattice. Devices with surface sulfidation retained more than 90% of the initial PCE after aging at 85°C for 2200 hours or operating at the maximum power point under continuous illumination for 1000 hours at 55° ± 5°C.
RESUMEN
PbI2 is a commonly used passivator for defect passivation in perovskite solar cells (PSCs). However, the poor conductivity nature of PbI2 may limit the further improvement of device performance. Here, we report a radical form of PbI2 with high conductivity to passivate defects for efficient PSCs through a combination of N,N,N',N'-tetramethylbenzidine (TMB). When PbI2 is combined with TMB, 4 orders of magnitude higher conductivity will be achieved owing to the formation of a TMB-PbI2 radical. As a result, the device performance is impressively increased from 20.48 to 22.63%. In addition, the device stability is also greatly improved and 95% of the initial efficiency is retained after aging at 85 °C for 600 h.
