UCLA researchers in the Department of Materials Science and Engineering have developed a novel lead halide perovskite solar cell based on a mixture of formamidinium perovskites and 2D perovskites.
Lead halide perovskite solar cells offer excellent photovoltaic efficiencies (up to 15%), but the perovskite material suffers from poor stability, resulting in device degradation within days. Compositional engineering is an important approach to enhance the stability and performance of perovskite solar cells. Typical high efficiency devices incorporate formamidinium (FA) cations, Cs, Rb and Br into perovskites. For example, incorporating FA forms a cubic FAPbI3 phase with a lower bandgap (Eg= 1.48 eV), higher absorption coefficient and longer carrier diffusion lengths than methylammonium (MA) based tetragonal MAPbI3 (Eg=1.57 eV). However, such compositional engineering has enhanced the open circuit voltage and stability at the expense of the short circuit current due to the increase in band gap size.
Professor Yang and his research team have developed highly efficient and stable perovskite solar cells and light emitting diodes based on formamidinium perovskite mixed with 2D perovskites. These phase-pure FAPbI3 films demonstrate improved crystallinity and an order of magnitude enhanced photoluminescence lifetime. Moreover, the 2D perovskites protect the FAPbI3 from moisture, resulting in significantly enhanced moisture stability. Devices reached a power conversion efficiency (PCE) of 21.06% (stabilized PCE of 20.64%). This device also achieved a high efficiency under Newport Corporation’s certified stabilized efficiency standard. The device retains 98% of initial PCE for 1392 h (58 days) storage under ambient condition.
Perovskite solar cell, 2D perovskites , formamidinium (FA) solution processable, high stability, solar cells, photovoltaic devices, opto-electronics, LEDs