ABSTRACT
An all-inorganic lead-free tandem PV cell consisting of two sub-cells CsSn0.5Ge0.5I3 (perovskite) based top cell/CIGS-based bottom cell has been designed, simulated, and optimized by varying the thickness of pertinent layers utilizing the SCAPS-1D simulator. In the top sub-cell, a wide bandgap lead-free inorganic CsSn0.5Ge0.5I3 perovskite is inserted as the primary absorber layer because of its distinctive characteristics with an ETL of ZnO, which is recognized for its high electron mobility & absorption coefficient, and an HTL of NiO to offer increased hole mobility with good chemical-durability. For the bottom sub-cell, we have selected p-type CIGS as the absorber with Spiro-OMeTAD as the apposite HTL to provide suitable offsets of valence and conduction band distribution and TiO2 as ETL to offer low-cost, low-ecotoxicity, excellent optical properties, and chemical-stability and thus offers improved efficiency of the overall tandem structure. In the beginning, the two sub-cells were simulated independently; the top sub-cell was simulated under the standard spectrum of AM1.5G, while the bottom sub-cell was optimized using a filtered spectrum. Thereafter, the current matching point of both cells was attained by optimizing the absorber layer thicknesses. Finally, our computational modeling and simulation results offer the optimized cell structure revealing an outstanding overall 38.39% power conversion efficiency (PCE), Fill Factor (FF) of 83.4%, open-circuit voltage (VOC) of 2.48 V, and short-circuit current density (Jsc) of 18.64 mA cm-2. The proposed tandem structure's performance matrices outperform those stated in the most recent literature. These outcomes of the proposed structure are expected to facilitate the development and production of a low-cost and highly effective inorganic perovskite Tandem PV cell in the future.
ABSTRACT
In this work, an ultra-thin (0.815 µm) lead-free all-inorganic novel PV cell structure consisting of solid-state layers with the configuration SnO2/ZnOS/CsGeI3/CZTSe/Au has been optimized using SCAPS-1D simulator. ZnOS electron transport layer (ETL) has been deployed and various hole transport layer (HTL) material candidates have been considered to find the most suitable one in order to get the maximum possible power conversion efficiency (PCE). The simulation begins with the optimization of the thickness of the ZnOS buffer layer, followed by an analysis of HTL and ETL doping concentrations, thickness and bandgap optimization of absorber layer. The maximum permissible defect density at the ZnOS/CsGeI3 interface and the bulk defect density of the absorber layer (CsGeI3) are also investigated. It is also found that when the temperature rises, short circuit current density (J sc ) rises by 1.43 mA/K and open-circuit voltage (V oc ) degrades by 2 mV/K. The optimized structure results in a PCE of 26.893% with J sc , V oc , and fill factor (FF) of 28.172 mA cm-2, 1.0834 V, and 88.107% respectively. The cell performance parameters outperform those found in the recent literature. The simulated results of the proposed configuration are expected to be a helpful reference for the future implementation of a cost-effective and efficient all-inorganic perovskite PV cell.
