Comparing the effect of P3HT and Spiro-OMeTAD as hole transport material in Sb2S3-based solar cells

Abstract

Background: The n-i-p structured Sb2S3 solar cells are widely developed based on various conditions of fabrication. Generally, these types of solar cells consist of different layers. Even though a high quality of the absorber layer (Sb2S3) is synthesized, the compactness of each layer is beneficial to enhance the performance. In this solid-state solar cells, the Hole Transport Material (HTM) is an attractive factor due to the commercialization difficulty of liquid electrolyte solar cells. Objectives: In this study, Sb2S3 solar cells were fabricated with P3HT and Spiro, which were used as HTMs to extract the holes from the absorber to find the effect of HTMs in our system. Methods: To fabricate the device configuration of FTO/TiO2/Sb2S3/HTM/Ag, a mixture of titanium isopropoxide, butan-1-ol, and 2-ethanolamine and a mixture of SbCl3, thiourea, and 2-methoxyethanol used to deposit TiO2 and Sb2S3 layers respectively. The P3HT and Spiro solutions were prepared by dissolving 2 mg of P3HT in 100 l of chlorobenzene and 3.6 mg of spiro-OMeTAD, 1.4 l of 4-tert-butyl pyridine (tBP), and 0.8 l LiTFSI solution (520 mg LiTFSI in 1 ml of acetonitrile) in 100 l of chlorobenzene respectively. The prepared HTM precursors were spin-coated separately on Sb2S3/TiO2 at 3000 rpm for 30 s and heated on the hotplate at 100 oC for 15 mins. Results: The power conversion efficiency (PCE) was obtained as % and % for the cell with spiro and P3HT respectively, by the current density (J)-voltage (V) measurements. A good current density (J) was received by Spiro (15.6 mA/cm2) than P3HT (14.05 mA/cm2), which enhanced the PCE. The EQE exhibited a wide range of spectrum for spiro-OMeTAD than P3HT, which was in good agreement with J. Conclusion: In our system, the photo-generated electron-hole pairs are effectively separated by Spiro-OMeTAD than P3HT. The HTM plays a significant role to improve the PCE of solar device.