چكيده به لاتين
The electron transport layer (ETL) plays an important role in determining the device performance of perovskite solar cells (PSCs). Recently, SnO2 has been used extensively as an ETL due to its many outstanding optoelectronic properties. Therefore, in this project, we investigated and optimized the SnO2 layer as the electron transport layer in the perovskite solar cell. We reported that UVO treatment for 25 minutes is an important process to improve PSCs based on SnO2 ETL performance.The wettability of UVO treated SnO2 is well-matched with the polar solvent of the perovskite solution, leading to complete coverage of the substrate. To improve the function of solar cells, we investigated SnO2 treatment by NH4F and NH4Cl as an ETL in a low-temperature solution process. In contrast to pure SnO2, the I-V curve and transmittance spectra show a significant conductivity improvement of treated SnO2 without declining the light transmittance property. Meanwhile, treated SnO2 could increase the electron transfer and decrease the recombination probability at the SnO2/perovskite interface, as well as passivate the electron traps, leading to the improvement in the PSC performance. Through a series of optimization methods, the best device based on NH4F treated SnO2 shows a power conversion efficiency (PCE) of 18.62%, with an open-circuit voltage (VOC) of 1.08 V, a short-circuit current density (JSC) of 21.83 mA/cm2, and a fill factor (FF) of 0.80 while pure SnO2 has a PCE of 14.47%, a Voc of 1.09 V, a Jsc of 19.82 mA/cm2, and a FF of 0.67. Therefore, SnO2 treatment with a suitable NH4F content is a promising candidate as an ETL for fabricating high-efficiency PSCs via the low-temperature process.
Meanwhile, SnS2 is considered one of the promising layered materials with excellent visible light absorption and electrical properties. Based on the properties of SnS2, we focused on the spin-coated tin (IV) sulfide (SnS2) as ETL with two different sulfur sources, thiourea (TU) and thioacetamide (TAA), (SnS2(TU) and SnS2(TAA))and investigated the effects of surface passivation of ETLs with TU and TAA. SnS2¬(TU)-TAA ETL exhibits a better energy alignment with the perovskite layer and improved electron mobility, which will promote efficient electron transfer at the interface. The best results were related to the samples with the ETL as SnS2(TU) passivated with TAA (SnS2(TU)-TAA) in which the power conversion efficiency (PCE) promoted from 11.98% in the case of SnS2(TU) ETL to 15.14% in SnS2(TU)-TAA ETL (with a 37% increase in PCE).
