Two-inch-sized perovskite crystals, CH3 NH3 PbX3 (X=I, Br, Cl), with high crystalline quality are prepared by a solution-grown strategy. The availability of large perovskite crystals is expected to transform its broad applications in photovoltaics, optoelectronics, lasers, photodetectors, LEDs, etc., just as crystalline silicon has done in revolutionizing the modern electronics and photovoltaic industries.

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Regulating the temperature during the direction contact and intercalation process (DCIP) for the transition from PbI2 to CH3NH3PbI3 modulated the crystallinity, crystal grain size and crystal grain orientation of the perovskite films. Higher temperatures produced perovskite films with better crystallinity, larger grain size, and better photovoltaic performance. The best cell, which had a PCE of 12.9%, was obtained on a film prepared at 200 °C. Further open circuit voltage decay and film resistance characterization revealed that the larger grain size contributed to longer carrier lifetime and smaller carrier transport resistance, both of which are beneficial for solar cell devices.

Color-tuned perovskite films have been recognized as a promising candidate for building integrated photovoltaics; bright, colorful displays; and component cells in multijunction solar cell applications. In this paper, four representative color-tuned perovskite films with chemical formula CH 3 NH 3 PbBr x I 3−x (x = 0, 1, 2, and 3) are successfully prepared by using a technique that combines the advantages of direct contact lead halide film with hot methylamine halide powder and intercalcation processes. The energy-dispersive X-ray spectrometry results indicate that the Br/I ratio is controlled as desired. The scanning electron microscopy imaging shows very uniform films with good surface coverage on the substrate. The highest power conversion efficiency of the perovskite solar cells with the four different compositions are 12.76%, 6.84%, 4.12%, and 3.53%, respectively.

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