Low Temperature Sintering of Polycrystalline Hybrid Organic-Inorganic Perovskites

Hybrid organic-inorganic perovskites [HOIPs] (ABX₃; A=CH₃NH₃, CH(NH₂)₂, Cs; B=Pb, Sn; X=Cl, Br, Cl) embody intriguing optoelectronic properties (e.g. tunable bandgaps, high absorption coefficients, and large charge carrier mobilities). However, many target applications for these semiconducting materials (e.g., scintillators, lasers, and photodetectors) require large area, millimeter thick perovskite single crystals with high optically transparency. Unfortunately, single crystals grown by melt-based approaches are limited to all-inorganic perovskites due to organic cation volatility, and solution-based methods are inundated with scalability and reproducibility issues. Sintering HOIP powders into high relative density (>0.999) polycrystalline wafers under an applied uniaxial pressure is a promising route towards overcoming the current limitations of melt and solvothermal single crystal growth. We demonstrate low temperature (~20 ^oC) sintering methods under an applied uniaxial pressure to compress high purity HOIP powders into high density, polycrystalline wafers with optical transparency and charge transport properties akin to their ideal single crystal counterparts. Structural, optical, and electrical properties of HOIP wafers are benchmarked against single crystals analogues. Fully understanding the tradeoff between manufacturability of polycrystalline wafers versus the performance of single crystals could enable key advancements in perovskite technologies.