Numerical analysis and design of high performance HTL-free antimony sulfide solar cells by SCAPS-1D

Among the various absorbers encountered in thin film solar cells (TFSCs), antimony sulfide (Sb2S3) is considered a suitable candidate as it is a non-toxic and earth-abundant besides its high absorption coefficient. However, some critical issues cause its poor photovoltaic performance. These include unoptimized Sb2S3 layer, interface recombination and cell properties like the ineffective carrier collection and transport. To enhance the power conversion efficiency (PCE) of Sb2S3 solar cell, we suggest some design guidelines by employing device simulation. First, a calibration step is performed vs an experimental arrangement consists of FTO/TiO2/Sb2S3/Spiro-OMeTAD/Au to validate the simulation model. Next, as the organic hole transport material (HTM) often has poor long-term operation stability and demands high-cost fabrication processes, an HTL-free cell is proposed and designed by investigating the impact of the main technological and physical parameters. In the first step in the design of the HTL-free cell, we provide an affinity engineering methodology to tune the conduction band offset between the electron transport layer (ETL) and the absorber. Based on this approach, the most appropriate electron transport material (ETM) is chosen that fulfills the maximum efficiency. Then, an optimization routine is performed to select the most appropriate design parameters and the PCE of the optimized case is found to be about 22%. All simulations, carried out in this work, are performed by SCAPS-1D device simulator under AM1.5G illumination and 300 K temperature.