Lanthanide-containing polyoxometalate as luminescent down-conversion material for improved printable perovskite solar cells

Full utilization of the incident light is an effective strategy to enhance photovoltaic performance of perovskite solar cells (PSCs). Here, we used lanthanide-containing polyoxometalate Na9[EuW10O36] (EuW10) as a luminescent down-conversion material incorporated in mesoporous TiO2 layer for boosting the power conversion efficiency (PCE) of the printable hole transport material-free PSCs. The EuW10 can convert the high energy photons into the low energy visible photons matched well with the absorption of perovskite, so that photogenerated current carriers increase substantially. This research represents the first example of using lanthanide-containing polyoxometalate as down-conversion materials to effectively improve PCE in solar cells. Compared with pristine TiO2 based PSCs, the EuW10-TiO2 based PSCs showed an enhanced power conversion efficiency (PCE) from 11.42% to 14.36% and obtained a remarkable photocurrent density of 23.46 mA/cm2. Besides, the EuW10-TiO2 based device exhibited a better long-term stability, which could maintain 98% initial efficiency after storage for 14 days. Since the efficiency of the printable perovskite solar cells has been a key factor to achieve commercial implementations, we consider that the results from this work demonstrate a new kind of down-conversion materials to boost PCE and stability. [Display omitted] •EuW10 is used as down-conversion material in the printable perovskite solar cells for the first time.•The PCE of EuW10-TiO2-based device is boosted from 11.42% to 14.36% as compared to that of TiO2-based device.•EuW10 could convert UV light into visible light so as to increase photogenerated current carriers.•An extremely high photocurrent density of 23.46 mA/cm2 is obtained.