Mixed perovskite (MAPbI3-xClx) solar cells using light-emitting conjugated polymer DMP end-capped MDMO-PPV as a hole transport material

Abstract

A series of solar cells (SCs) with methylammonium mixed halide perovskite active layers with a conjugated polymer (CP) poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene] and end-capped with dimethylphenyl (MDMO-PPV) as a hole transport material (HTM) was fabricated under the same experimental settings, and the performance characteristics of the individual cells were compared. For comparison purposes, we fabricated a perovskite solar cell (PSC) with a lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI)-doped sprio-OMeTAD layer (LiTSO), which showed a power conversion efficiency (PCE) of 7.68 %. The layered solar cell with a structure of TiO2, perovskite and MDMO-PPV layers showed a PCE of 5.32 % and a fill factor of 0.478. The heterojunction solar cell (HJSC) made with a perovskite and MDMO-PPV mix showed a PCE of 5.68 %. The Field emission scanning electron microscope (FESEM) showed that in HJSC, the perovskite and CP were mixed well. However, they did not penetrate deeply into the TiO2 mesoporous layer, which would hinder electron transportation and thus cause efficiency loss. The HJSC structure was tested using different thicknesses of mesoporous TiO2 (m-TiO2). At an optimal m-TiO2 thickness, the blend of perovskite and MDMO-PPV infused up to 350 nm, thus improving the PCE to 7.438 % and retaining 91 % performance even after 4 weeks of continuous operation. The perovskite/conjugated polymer blend also formed a small SC above the m-TiO2 layer, showing complete penetration of the perovskite into the m-TiO2 layer. Additionally, the formation of a pure perovskite layer on top of the TiO2/perovskite and MDMO-PPV covers neatly on top of the perovskite layer and serves as a protective layer as well as a hole transport layer. An additional layer of LiTSO on top of the HJSC further improved the PCE to 7.76 %. The use of a CP as the hole transport layer reduces the dependency on separate materials and improves the device’s stability. It could also pave the way for an easy minimalistic method for integrated, flexible power electronics that contain solar cells (perovskite/conjugated polymer), organic light-emitting diodes, and supercapacitors made of graphene.