Improved Efficiency of Perovskite Solar Cells with Low‐Temperature‐Processed Carbon by Introduction of a Doping‐Free Polymeric Hole Conductor

Abstract

Low‐temperature‐processed carbon‐based perovskite solar cells (C‐PSCs) are promising photovoltaic devices, because of their good stability, low cost, and simple preparation methods, which allow for scalable processing. Herein, C‐PSCs with the n−i−p structure are prepared, using a SnO 2 nanoparticles film as the electron‐selective contact, MAPbI 3 perovskite as the intrinsic absorber layer (MA = methylammonium), and a carbon layer as the hole‐selective layer and conductor. Carbon is, however, not an ideal hole‐selective layer and it is found that improved solar cell performance can be obtained by introducing a polymeric hole conductor between the perovskite and the carbon layer. Specifically, undoped poly(3‐hexylthiophene) (P3HT) is used for this purpose, as it is stable and highly hydrophobic. For ITO/SnO 2 /MAPbI 3 /carbon devices, a solar cell efficiency of up to 12.8% is obtained, increasing up to 15.7% with the inclusion of a P3HT layer, which increases open‐circuit potential, photocurrent, and fill factor (FF). In comparison, ITO/SnO 2 /MAPbI 3 /P3HT/Au devices performed rather poorly (up to 11.7%). Encouraging stability is obtained for unencapsulated C‐PSC devices: P3HT/carbon devices do not show any degradation in solar cell performance upon storage for 1 month in low humidity, while they maintain 70% of their initial efficiency after 900 h at 82 °C in air.