The hybrid organic inorganic perovskite (HOIP) team at NREL has the ability to grow high-quality hybrid perovskites for various solar conversion and optoelectronic applications. The typical hybrid perovskite materials have an ABX3 structure, where A is monovalent cation such as methylammonium (MA+), formamidinium (FA+), or cesium (Cs+); B is a bivalent cation such as Pb2+ or Sn2+; and X is a halide anion such as I-, Br-, or Cl-. The NREL HOIP team is capable of producing >20% perovskite solar cells with either a normal n-i-p (e.g., glass/TCO/ETL/perovskite/HTL/Ag; ETL/HTL: electron/hole transport layer) or an inverted p-i-n (e.g., glass/TCO/HTL/perovskite/C60/BCP/Ag) device structures for different applications. The bandgap of perovskites can be varied from about 1.2 eV to 2.3 eV by changing A-, B-, and/or X-site compositions. These perovskites can be synthesized in various forms including polycrystalline thin films, single crystals, and nanocrystals. In addition to the standard 3-dimensional (3-D) perovskite ABX3 structure, the NREL HOIP team also has expertise on fabricating 2-D or quasi 2-D perovskites with a general structure of (R-NH3)2An-1BnX3n+1, where n=1 corresponds to a 2-D perovskite sheet whereas n=∞ corresponds to the 3-D perovskite structure. It is worth noting that the NREL HOIP team can produce >20%-efficient solar cells with a wide range of perovskite bandgaps including ~1.7 eV perovskite composition which is suitable to pair with Si or similar bandgap materials for tandem devices. The wide selection of material compositions and continuous bandgap tuning coupled with high conversion efficiencies are very attractive for PEC applications especially tandem or multijunction PEC electrodes or hybrid photo-electrodes for H2 production.

As part of HOIP solar cells fabrication, the team also has physical vapor deposition (PVD) capabilities for the 3D perovskite active layer materials across the typical photovoltaic material composition space, as well as oxide or metal contact layer materials. The PVD tools include traditional magnetron based sputtering which can be used to produce single or mixed composition materials and multilayers for 3-4 1”x1” samples or fixed compositions at larger areas up to 5”x5” for typical transparent oxides (e.g, IZO, GZO). More flexible PVD capabilities that can also be leveraged for custom electrode depositions also includes pulsed laser deposition which can handle up to 2” x 2” and permits graded oxide composition electrodes, complex multilayers contacts to be deposited. Critical to many of these is production of thin protective layers which permit integration of PVD based materials without compromising the HOIP materials via atomic layer deposition (ALD) or related chemical vapor deposition. ALD can also be used as a means of creating encapsulation for improved perovskite stability alone or in combination with other PVD layers. Metal deposition, as well as select dielectric oxides, can be done via thermal or e-beam deposition capabilities; again these can be used as electrodes and/or encapsulation layers. These various materials also enable both integration of multiple absorbers for multijunctions and serve as electrodes for integration of catalysts for hydrogen evolution.