Modeling of Ag incorporated Sb₂(S_xSe_1−x)₃ bi-layer devices: Enhanced bi-layer absorber configuration

In this contribution, we proposed Ag incorporated Sb₂(S_xSe_1−x)₃ bi-layer solar cells by modeling and simulation to optimize the absorber layer. Firstly, as the sulfur composition increases, we have investigated simple single-layer devices with the absorber film of each AgSb(S_xSe_1−x)₃ and Sb₂(S_xSe_1−x)₃ as a frame of reference. Secondly, the impact of sulfur composition on bi-layer devices has been studied with two different absorber configurations such as Sb₂(S_xSe_1−x)₃/AgSb(S_xSe_1−x)₃ and AgSb(S_xSe_1−x)₃/Sb₂(S_xSe_1−x)₃. Compared with any single-layer devices, the absorber configuration of AgSb(S_0.4Se_0.6)₃/Sb₂(S_0.4Se_0.6)₃ bi-layers shows best performance at the sulfur composition, x = 0.4. This is caused by the reduced effective Schottky barrier (by 126 mV) at the back contact, improving the roll-over effect by 4.3 times at 1 V. The resulting efficiency is 18.6 %, Voc (778.9 mV), Jsc (37.2 mA/cm²), and FF (64.0 %). Once the devices with highest efficiency and the optimal sulfur composition are identified, a set of different device parameters have been studied to optimize these bi-layer devices further. With AgSb(S_0.4Se_0.6)₃/Sb₂(S_0.4Se_0.6)₃ bi-layer devices, the result from various doping concentration of each bi-layers indicates that doping concentration of AgSb(S_0.4Se_0.6)₃ is responsible for Jsc, while the doping concentration of Sb₂(S_0.4Se_0.6)₃ dictates Voc under certain doping concentration of AgSb(S_0.4Se_0.6)₃ (approximately 1 × 10¹⁵/cm²). The best efficiency is 21.4% with Voc (822 mV), Jsc (38.1 mA/cm²), and FF (68.4%).