engleski

Passivation of electron transport layer to achieve better efficiency of perovskite solar cells

High efficiency perovskite solar cells (PSC) rely on successful interplay of considerable amount of thin films constituents. Configuration of PSC reposes on bottom electrode (transparent metal oxide such as indium tin oxide or aluminium doped zinc oxide) ; electron transfer layer (ETL) ; active layer ; hole transport layer and top electrode. Among ETL layers, titania stands out, particularly if utilised in mesoporous or nanostructured morphology. However, titania films have one major drawback: they require a substantial thermal treatment step (over 400 °C). Zinc oxide, having similar physical, chemical and optical properties as titania, can be easily derived by numerous room temperature low-cost chemical methods. Nevertheless, ZnO films have shown to be susceptible to induce degradation of the active perovskite layer, which can be easily overcome by using a buffer layer, such as titania. This work compares conventional approaches with those deriving nanostructured thin-films of zinc oxide, that were additionally modified by a ~50 nm titania. The titania layer was deposited by several physical (magnetron sputtering and pulsed laser deposition) and chemical deposition methods (sol-gel and spin coating). PSCs were prepared and tested immediately after closure in protective atmosphere. Electrical measurements showed that the devices continuously showed high current and voltage but had limited success for achieving higher fill factors. Scanning and transmission electron microscopies (SEM and TEM) confirmed successful fabrication of the core shell type of ETL layer, and effective infiltration with the active perovskite layer. The best results were achieved for the core shell zincite nanorods and titania coating derived by chemical method. The reason for that lies in the fact the coating was employed using titania sol, which facilitated better coverage of the rods, subsequently better PCE of the solar cells.

solar cells ; perovskites ; ZnO

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