Boosting the Performance of One-Step Solution-Processed Perovskite Solar Cells Using a Natural Monoterpene Alcohol as a Green Solvent Additive

The perovskite film is the core of a perovskite solar cell (PSC), and its quality is crucial for the performance of such devices. The morphology, crystallinity, and surface coverage of the perovskite layer greatly affect the power conversion efficiency (PCE), hysteresis, and long-term stability of PSCs. The incorporation of appropriate solvent additives in the perovskite precursor solution is an effective strategy to control the film morphology and reduce the defects and grain boundaries. However, the commonly used solvent additives are environmentally harmful and highly toxic. In this work, α-terpineol (a nontoxic, eco-friendly, and low-cost monoterpene alcohol) is employed for the first time as an alternative green solvent additive to improve the quality of one-step solution-processed CH3NH3PbI3–xClx films and to restrain nonradiative recombination in the corresponding devices. An in-depth investigation of the physicochemical effects induced by such a high-boiling-point, polar protic solvent when incorporated into a conventional perovskite solvent system is provided. The collected data demonstrate that the addition of a precise amount of α-terpineol can generate uniform and highly crystalline perovskite films with improved photovoltaic performances. Through this approach, the PCE of planar n–i–p PSCs is boosted up to 17.5% (against 16.1% of the top control device) with reduced hysteresis and enhanced ambient stability.