**Composited Film of Poly(3,4-ethylenedioxythiophene) and Graphene Oxide as Hole Transport Layer in Perovskite Solar Cells**

**Tian Yuan, Jin Li \* and Shimin Wang \***

Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China; tianyuan@stu.hubu.edu.cn **\*** Correspondence: jinli@hubu.edu.cn (J.L.); shiminwang@126.com (S.W.)

**Abstract:** It is important to lower the cost and stability of the organic–inorganic hybrid perovskite solar cells (PSCs) for industrial application. The commonly used hole transport materials (HTMs) such as Spiro-OMeTAD, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and poly(3-hexylthiophene-2,5-diyl) (P3HT) are very expensive. Here, 3,4-ethylenedioxythiophene (EDOT) monomers are in-situ polymerized on the surface of graphene oxide (GO) as PEDOT-GO film. Compared to frequently used polystyrene sulfonic acid (PSS), GO avoids the corrosion of the perovskite and the use of H2O solvent. The composite PEDOT-GO film is between carbon pair electrode and perovskite layer as hole transport layer (HTL). The highest power conversion efficiency (PCE) is 14.09%.

**Keywords:** perovskite solar cell; hole transport layer; carbon materials; polymeric composites; solar energy materials
