An Aromatic Diamine Molecule as the A-Site Solute for Highly Durable and Efficient Perovskite Solar Cells

Studies of organometallic perovskite solar cells have remarkably progressed within several years, but there still remain concerns of poor stability and insufficient power conversion efficiency (PCE). To overcome these limitations, modification of the perovskite material should be addressed. Herein, imidazole (C3H4N2) is demonstrated as an A-site solute for the conventional methyl-ammonium lead iodide (CH3NH3PbI3). As an aromatic hydrocarbon and diamine species with a small ionic radius, imidazole is appropriately alloyed and the bond interactions within the ABX(3) lattice are increased. Also, the nature of delocalized pi bonding and the unique structure of imidazole allow the formation of an unprecedented kind of hybrid perovskite exhibiting favorable band alignment and optical propertie with high electrical conductivity. Optimal content of imidazole incorporated into CH3NH3PbI3 with architectural optimization of the device leads to improved PCEs approaching 20.2% (reverse) with small hysteresis (forward PCE = 19.0%). Furthermore, properly alloyed imidazole into the A-site of CH3NH3PbI3 leads to extra stability against air, light, and heat. Lastly, devices with a large active area of 2 cm(2) exhibit PCEs as high as 16.8%, further addressing the effect of imidazole on the formation of high quality nanostructured perovskite and devices.