| 초록 |
Organometallic halide perovskite solar cells have drawn increasing attention due to their outstanding photovoltaic properties. The great increase of power conversion efficiency (PCE) of perovskite solar cells was led by the introduction of intermediate phase that originated from the Lewis acid-base reaction. The use of dimethyl sulfoxide (DMSO), one of the most widely conjugated Lewis base solvent, led the improvement of morphology of perovskite layer by decreasing the nucleation rate and consequently separating the nucleation from grain growth. However, DMSO accompanied the unsought defects in the bulk perovskite and the interfaces due to the transition from intermediate phase to perovskite. In this work, we fabricated the perovskite layers using different Lewis base precursor solvents and evaluated the crystallinity, morphology, defect density, and PCE. From the mono-solvent precursor based on dimethyl formamide (DMF), DMSO, and a solvent with a lower Lewis basicity, the formation of intermediate phase and perovskite nuclei was observed. Subsequently, using the mixed-solvent precursors, photovoltaic properties, defect density at bulk and interfaces were compared. Perovskite layers derived from direct formation of perovskite nuclei without intermediate phase after spin-coating showed a low trap density, long charge carrier lifetime, and eventually reduced hysteresis in the perovskite solar cells. The champion cell based on CH3NH3PbI3 with low donor Lewis base solvent showed efficient PCE of 20.02% along with the improved open circuit voltage. This work suggests a careful perspective to design the precursor solvent during the fabrication of perovskite layer for efficient and hysteresis-free perovskite solar cells. |
