Space-Charging Interfacial Layer by Illumination for Efficient Sb₂S₃ Bulk-Heterojunction Solar Cells with High...

Solution-processed material systems for effective photovoltaic conversion are the key to low-cost and efficient solar cells. While antimony trisulfide (Sb₂S₃) is a promising photovoltaic absorber, solution-processed quality Sb₂S₃-based heterojunction systems for solar cells, particularly with an open-circuit voltage (V_oc) higher than 0.70 V, are challenging issues. Here, a cadmium sulfide (CdS) interfacial engineering method is developed for the Sb₂S₃-based bulk-heterojunction (BHJ) solar cells with an efficiency of 6.14% and a V_oc up to 0.76 V that is the highest one among solution-processed Sb₂S₃ solar cells. The prepared Sb₂S₃-based BHJ solar cells feature a Sb₂S₃ nanoparticle film interdigitated by a titania (TiO₂) nanorod array with a nanostructured CdS shell as an interfacial layer on each TiO₂ nanorod core. Upon understanding the interfacial interactions and band alignments in the TiO₂-CdS-Sb₂S₃ system, the function of the CdS interfacial layer as a band-bended spatial spacer interacting strongly with both the TiO₂ electron transporter and Sb₂S₃ absorber for increasing charge collecting efficiency is revealed; moreover, space-charging the band-bended CdS layer by illumination is found and a photogenerated interfacial dipole electric field model is proposed for understanding the high V_oc subjected to the presence of the CdS interfacial layer. This work provides a conceptual guide for designing efficient inorganic heterojunction solar cells.