Investigation on Buffer Layers Influence on the Internal Quantum Efficiency of CH<sub>3</sub>NH<sub>3</sub>Sn<sub>(1-y)</sub>Ge<sub>y</sub&gt

In this work, we have carried out a study in the modeling of photovoltaic devices based on lead-free perovskite materials, such as CH<sub>3</sub>NH<sub>3</sub>Sn<sub>(1-y)</sub>Ge<sub>y</sub>I<sub>3</sub>, in which the germanium content varies from 0 to 1, using thin ZnO, TiO<sub>2</sub> or SnO<sub>2</sub>, films as window layers. Thin Cu<sub>2</sub>O or NiO layers used as buffer layers ensure the n-p junction with the perovskite absorber material and act as an interface layer with the transport window layer. With the above window and buffer layer materials, photovoltaic devices have been designed. The study highlights the influence of geometric parameters such as the diffusion length of the minority carriers in the buffer layer as well as the thickness of this layer on the performance of photovoltaic devices. The evolution of the internal quantum efficiency is analyzed as a function of the window and buffer layer materials and also as a function of various other parameters including the thickness of the buffer layer materials and the minority carrier diffusion length in these materials. The results showed that NiO thin films offer better performances, especially when combined with ZnO or SnO<sub>2</sub> window layers, respectively. The corresponding models with structures ZnO(n<sup>+</sup>)/NiO(n)/CH<sub>3</sub>NH<sub>3</sub>Sn<sub>0.75</sub>Ge<sub>0.25</sub>I<sub>3</sub>(p) and SnO<sub>2</sub>(n<sup>+</sup>)/NiO(n)/CH<sub>3</sub>NH<sub>3</sub>Sn<sub>0.75</sub>Ge<sub>0.25</sub>I<sub>3</sub>(p) give an internal quantum efficiency of 72.7% and 70.9% respectively.