Improved performance of PCBM/MAPbI3 heterojunction photovoltaic cells with the treatment of a saturated BCP/IPA solution

The interfacial contact quality between the hydrophilic MAPbI3 and hydrophobic PCBM thin films are improved by using the treatment of a saturated bathocuproine/isopropanol (BCP/IPA) solution, which largely increases the power conversion efficiency (PCE) from 12.96% to 18.67%. The atomic force microscopic images, water-droplet contact angle images, viscosity measurement results and near-infrared transmittance spectra show that the increased open-circuit voltage (VOC) is related to the formation of a denser PCBM thin film and the better contact quality of the PCBM/MAPbI3 heterojunction. Besides, the power-dependent current density-voltage (J-V) curves show that the lower defect density in the solar cells results in the higher VOC. In other words, the treatment of a saturated BCP/IPA solution can decrease the defect density of the PCBM/MAPbI3 heterojunction and thereby boosting the photovoltaic performance and extending the device lifespan. •The saturated BCP/IPA solution treatment increases the density of the PCBM thin film.•The saturated BCP/IPA solution treatment strengthens the contact quality at PCBM/MAPbI3 interface.•The saturated BCP/IPA solution treatment increases the hydrophobicity of PCBM/MAPbI3 heterojunction.•The saturated BCP/IPA solution treatment improves the PCE of photovoltaic cells from 12.69% to 18.67%.