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The efficiency and the thermal stability enhancement in tin–lead (SnPb)-based perovskite solar cells (PSCs) was investigated in this study by employing germanium iodide (GeI2) as a doping agent. The incorporation of GeI2 enhanced the performance of GeI2-doped SnPb PSCs with the highest efficiency of 21.9%. The XPS depth profiling showed unique observation; the Ge layer was only formed on the surface of the SnPb films. This layer encapsulated the SnPb films and thus prevented the perovskite films from extreme oxidation and structural and morphological degradations. An interlayer engineering approach was adopted in order to prove the PSCs by employing MeO2PACz monolayer as the hole extraction layer, while the tin oxide (SnOx) layer fabricated via atomic layer deposition (ALD) was applied near the electron transport layer. More than 94% of the initial efficiency was retained after 1000 h of a thermal stability test conducted at 85 °C in nitrogen atmosphere in the champion device.
Sahamir et al. (Mon,) studied this question.