Stability-improved perovskite solar cells through 4-tertbutylpyridine surface-passivated perovskite layer fabricated in ambient air

Methylammonium lead iodide (CH3NH3PbI3) perovskite solar cell (PSC) is one of the third generations of photovoltaic (PV) research interest in recent years. The solar cell degrades very fast in ambient air and this poses major challenge for its commercialization. Hence, this report investigates surface-passivated perovskite layer using hydrophobic material, 4-tertbutylpyridine (tBP), to modify the surface of the perovskite layer and create ambient air-resistant layer that results in improved stability of PSC performance. The fabricated films and devices were studied using UV-Vis spectrophotometer, Fourier-transform infrared (FTIR) spectrometer, Scanning Electron Microscopy (SEM), solar simulator equipped with Keithley source meter and X-ray diffractometer (XRD). The concentration of tBP was varied from 50 to 200 mu l and the samples were aged in ambient air for 120 h. Eventually, the surface passivated film and the device showed improved stability performance. The champion cells of tBP-treated and untreated freshly fabricated devices showed PCE of 10.32% and 6.37%, respectively. Again, the PCE of tBP-treated and untreated devices reduced by 6.45% (10.32%-9.66%) and 60.75% (6.37%- 2.50%) respectively for 120 h. Additionally, continuous light-soaking for 8 h shows that tBP-treated device is stable in its performance when compare with the tBP-untreated device. The statistical analyses carried out showed that device PCE stability depended mainly on the device tBP treatment. Also, device treatment varies directly proportional to the PCE. The probability plot from the statistical analysis also showed that observed (experimental) data agreed with predicted data. Consequently, this work implies that ambient stability of perovskite solar cell can be achieved from surface-passivation of perovskite layer for commercialization of the PSCs.