Performance enhancement of a Ge-Sn Co-alloyed all-inorganic based perovskite solar cell using an organic hole transport layer

The urge and numerous efforts to develop more stable and efficient perovskite solar cells for commercialization have led to the use of germanium-tin co-alloyed Cesium-based perovskite (CsSn0.5Ge0.5I3). Contrary to extremely toxic lead and unstable tin-based perovskites, CsSn0.5Ge0.5I3 exhibits superior stability and is more ecologically friendly. In this study, a CsSn0.5Ge0.5I3 heterostructure having TiO2 and D-PBTTT-14 referred to as charge transport layers has been numerically investigated. D-PBTTT-14 was introduced as a HTL because of its higher stability in comparison to other organic hole transport materials. Furthermore, the electric field generated and the perovskite layer's staggered band-alignment with D-PBTTT-14 accentuates the importance of the HTL in increasing efficiency. For the improvement of the designed solar cell several parameters were studied: thickness, defect density, series resistance, and shunt resistance. The simulated results in the present study suggest that the 100 nm-thick hole transport layer and 1.5 μm thick perovskite absorber layer offers the highest light harvesting efficiency of 30.27 % with a Jsc of 28.31 mA/cm2, Voc of 1.24 V, and a FF of 85.90 %.