Exploring solar cell performance of inorganic Cs₂TiBr₆ halide double perovskite: A numerical study

With a high power-conversion efficiency (PCE) of over 23%, perovskite solar cell (PSC) technology holds a viable trajectory for commercialization. Despite its attractive features, the use of lead and degradable components in the device need to be addressed. To this end, we have carried out simulation studies to explore a non-toxic and inorganic device utilizing Cs₂TiBr₆ as the active layer and Cu₂O as the hole transport layer (HTL). We have investigated a few of the most critical areas of device physics to glean insights into possible ways of improving the performance of such a viable technology. A PCE of 14.68% (open-circuit voltage Voc of 1.10 V, short-circuit current Jsc of 25.82 mA/cm², and fill factor FF of 51.74%) was obtained at an optimal perovskite layer thickness of 800 nm. Our investigation further reveals that with increasing perovskite thickness, as J₀ (saturation current) decreases, Voc increases. By varying the radiative recombination rate, we quantitatively demonstrate an inverse relationship with PCE, and report out a PCE of 20.49% at a 100X lower than usual recombination rate. A PCE of 14.68% was obtained with an optimal work function of 5.1 eV for the metal back contact. A conduction band offset of −0.1 eV between the TiO₂ electron transport layer (ETL) and the active layer and a valence band offset of −0.4 eV between the active layer and the HTL produce optimal PCE values of 14.68% and 18.97% respectively. Lastly, we demonstrate that Cs₂TiBr₆ is more sensitive to defect density than the device HTL and ETL by a factor of 10.