120 mm single-crystalline perovskite and wafers: towards viable applications

As the large single-crystalline silicon wafers have revolutionized many industries including electronics and solar cells, it is envisioned that the availability of large single-crystalline perovskite crystals and wafers will revolutionize its broad applications in photovoltaics, optoelectronics, lasers, photodetectors, light emitting diodes (LEDs), etc. Here we report a method to grow large single-crystalline perovskites including single-halide crystals: CH₃NH₃PbX₃ (X=I, Br, Cl), and dual-halide ones: CH₃NH₃Pb(Cl_xBr_1−x)₃ and CH₃NH₃Pb(Br_xI_1−x)₃, with the largest crystal being 120 mm in length. Meanwhile, we have advanced a process to slice the large perovskite crystals into thin wafers. It is found that the wafers exhibit remarkable features: (1) its trap-state density is a million times smaller than that in the microcrystalline perovskite thin films (MPTF); (2) its carrier mobility is 410 times higher than its most popular organic counterpart P3HT; (3) its optical absorption is expanded to as high as 910 nm comparing to 797 nm for the MPTF; (4) while MPTF decomposes at 150 °C, the wafer is stable at high temperature up to 270 °C; (5) when exposed to high humidity (75% RH), MPTF decomposes in 5 h while the wafer shows no change for overnight; (6) its photocurrent response is 250 times higher than its MPTF counterpart. A few electronic devices have been fabricated using the crystalline wafers. Among them, the Hall test gives low carrier concentration with high mobility. The trap-state density is measured much lower than common semiconductors. Moreover, the large SC-wafer is found particularly useful for mass production of integrated circuits. By adjusting the halide composition, both the optical absorption and the light emission can be fine-tuned across the entire visible spectrum from 400 nm to 800 nm. It is envisioned that a range of visible lasers and LEDs may be developed using the dual-halide perovskites. With fewer trap states, high mobility, broader absorption, and humidity resistance, it is expected that solar cells with high stable efficiency maybe attainable using the crystalline wafers.