The completely dissolved perovskite PbI2 solution in a solnvent is obtained by heating it around 60 degree by keepint it in a oil bath until it dissolves fully. However, the solution contains the presence of colloidal particles (due to tyndall effect). And this is essential for crystal growth. At last, the perovskite solution was heated in oil bath at 152 °C for 3-4 hours to get 3mm size of a crystal. In order to obtain larger crystals, the seed is removed and placed in a fresh perovskite solution to continue growing. Larger crystals were obtained in 3 hours . By repeating this step, a crystal of desired size can be obtained. However, in the process of growing crystals, the temperature needs to be constantly adjusted. When the temperature is below 150 °C, the growth of the crystal is small and irregular. When the temperature is higher than 160 °C, the crystal is large, but irregular. And the temperature is too high, the cap is easy to loose so as to affect the crystallization. Therefore, 152 °C is appropriate to grow large and regular crystals.

Thank you Dr. Krishnakumar. Did you use any acid to catalyse the reaction (Eg: Formic acid). While separating the seed crystals do I have to take any precautions. Can I directly keep the the seed crystal in the fresh perovskite solution, or should I keep any substrate at the bottom. Thank you in advance.

 good answer Krishnakumar Muthusamy

Thank you. Keeping substrate work sometime. Based on material we may use substrate. But filtered solution alone is preferred for inclusion free crystal growth. Impurities in substrate will contaminate the solution.in my perspective no need for catalyst. Best wishes