Abstract
As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic–inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thickness of each layer was controlled on molecular layer scale by programming the evaporation IR laser pulse number, length, or power. The layer thickness was monitored with an in situ quartz crystal microbalance and calibrated against ex situ stylus profilometer measurements. A computer-controlled movable mask system enabled the deposition of combinatorial thin film libraries, where each library contains a vertically homogeneous film with spatially programmable A- and B-layer thicknesses. On the composition gradient film, a hole transport Spiro-OMeTAD layer was spin-coated and dried followed by the vacuum evaporation of Ag electrodes to form the solar cell. The preliminary cell performance was evaluated by measuring I-V characteristics at seven different positions on the 12.5 mm × 12.5 mm combinatorial library sample with seven 2 mm × 4 mm slits under a solar simulator irradiation. The combinatorial solar cell library clearly demonstrated that the energy conversion efficiency sharply changes from nearly zero to 10.2% as a function of the illumination area in the library. The exploration of deposition parameters for obtaining optimum performance could thus be greatly accelerated. Since the thickness ratio of PbI2 and CH3NH3I can be freely chosen along the shadow mask movement, these experiments show the potential of this system for high-throughput screening of optimum chemical composition in the binary film library and application to halide perovskite solar cell.
Highlights
Halide perovskites, ABX3 (X=I, Br, Cl) have attracted much interest, ever since the demonstration of high photovoltaic energy conversion efficiency of methylammonium lead iodide: CH3NH3PbI3 (MAPbI3) cells [1]
We have developed an IR laser molecular beam epitaxy (MBE) system for organic– inorganic hybrid materials
The system is equipped with a movable mask that can be used for combinatorial deposition of composition or thickness gradient libraries
Summary
ABX3 (X=I, Br, Cl) have attracted much interest, ever since the demonstration of high photovoltaic energy conversion efficiency of methylammonium lead iodide: CH3NH3PbI3 (MAPbI3) cells [1]. This halide or organic–inorganic hybrid perovskite solar cell has fascinating physical properties [2,3,4,5,6,7] and there was a rapid increase of conversion efficiency from 3.8% in 2009 to. A major limitation of perovskite solar cells is the low stability of the crystal lattice and rapidly degrading cell performance [9,10,11]. Attempts to improve the properties of the halide materials have been undertaken; conventional one-by-one experiments [2,12,13,14,15,16,17] are very time consuming for exhaustive screening of the possible parameter space
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
