Sb2S3/TiO2 Heterojunction Solar Cells Based on Carbon Electrode with Higher Photocurrent

In Sb2S3 thin film solar cells, an organic material is typically used as the hole transport layer (HTL), while a noble metal grid is used for hole collection. However, the organic HTL often has poor stability during long-term operation and requires expensive materials. In this work, a carbon electrode is used as both the HTL and collection electrode in Sb2S3 solar cells. Electrochemical impedance spectroscopy showed that the carbon-electrode-containing device exhibited a smaller transfer resistance R-tr of 5.05 x 10(3) Omega compared with 1.41 x 10(4) Omega in a device based on poly(3-hexylthiophene-2,5-diyl)(P3HT) and Ag. This indicated that carbon has a better hole transfer from Sb2S3 to the cathode. Intensity-modulated photocurrent spectroscopy showed that the electron-hole transit time was reduced by almost half from the time of excitation to collection, which suggests that holes are more easily transferred from Sb2S3 to HTL. Moreover, hole transfer kinetics were investigated by transient absorption spectroscopy, which showed that the estimated hole transfer rate, k(ht), was 1.8 x 10(9) s(-1) at the Sb2S3/carbon interface, which is 2.43 times faster than 7.4 x 10(8) s(-1) at the Sb2S3/P3HT interface. These results indicate that the carbon electrode displays superior hole extraction from Sb2S3 compared to the P3HT/Ag electrode. (C) 2019 The Electrochemical Society.