Researchers from Saule Research Institute, Saule Technologies, Centre for Hybrid and Organic Solar Energy (CHOSE), CNR-SCITEC, Istituto Italiano di Tecnologia (IIT), Wroclaw University of Science and Technology, Bydgoszcz University of Science and Technology and Poznan University of Technology have demonstrated an effective strategy to improve the technical aspects of flexible perovskite solar cells, improving the reliability and efficiency values of these devices.
The team applies large organic ammonium molecules for modifying a buried interface between a hole-transporting layer (HTL) and perovskite-absorbing material. With the 4-fluorophenethylammonium iodide (FPEAI), they achieved 18.66% efficiency for the large-area (1 cm2) flexible solar cell, a significant improvement over the pristine device without modification.
The applied passivation strategy reportedly results in a better hole extraction and reduced nonradiative recombination loss at the buried interface.
Moreover, the scientists demonstrated the formation of low-dimensional perovskite phases in the vicinity of the hole-transporting material upon the incorporation of large ammonium cations. This results in a significantly enhanced thermal and light-soaking stability of fabricated devices.
They obtained no loss in 1000 h of aging at 85 °C, no loss in 1000 h of light soaking at open circuit, and less than 10% drop in 1000 h of operation at maximum power point for the optimized passivation treatment with the FPEAI.
They also demonstrated a method for monitoring the structural stability of perovskite thin films upon prolonged illumination, ensued by the amount of molecular iodine being released from the layer.