Preparation and Characterization of Mixed Halide MAPbI_3−xCl_x Perovskite Thin Films by Three‐Source Vacuum Deposition

Abstract

Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI3–xClx), but its persistence and role in solution‐processed materials has not yet been rationalized. Multiple‐source vacuum deposition of perovskites enables a fine control over thin‐film stoichiometry and allows the incorporation of chemical species irrespective of their solubility. Herein, the first example of mixed MAPbI3–xClx thin films prepared by three‐source vacuum deposition is presented using methylammonium iodide (MAI), PbI2, and PbCl2 as precursors. The optoelectronic properties of the material are evaluated through photovoltaic and electro‐/photoluminescent characterizations. Besides the very similar structural and optical properties of MAPbI3 and MAPbI3–xClx, an increased electroluminescence efficiency, longer photoluminescence lifetimes, as well as larger photovoltage, are observed in the presence of chloride, suggesting a reduction of nonradiative charge recombination.

Solvent-Free Method for Defect Reduction and Improved Performance of p-i-n Vapor-Deposited Perovskite Solar Cells

“…This may be due to fewer crystalline defects being present in the film grown with PbCl 2 or an active passivation effect of the Cl ions. The order of magnitude increase in photocarrier lifetimes is consistent with that of vapor deposited MAPbI 3 43 , 44 and MAPbI 3– x Cl x , 49 , 56 though even the latter only displayed TRPL lifetimes up to 83 ns. 49…”

“… 5 , 7 However, since chloride ions have a significantly smaller ionic radius than iodide ions, it is not immediately clear if the X site substitution is possible. Indeed, there has been much debate previously as to what extent Cl can substitute I in the similar MAPb(I 1– x Cl x ) structure, 2 , 51 − 56 with the most generous reports finding Cl can substitute only up to 3–4%. 51 Notably, MAPb(I 1– x Cl x ) 3 can be processed with a significant excess of chloride salts, yet most of the Cl is volatilized from the film in the form of MACl.…”

Blade-Coated Perovskites on Textured Silicon for 26%-Efficient Monolithic Perovskite/Silicon Tandem Solar Cells

“…The reduced reflection loss from the textured surface enabled a tandem with only 1.64 mA/cm 2 reflection loss and 25.2% efficiency. 25 Several groups have successfully developed one-step vacuum deposition processes for complex compositions of perovskite films, [26][27][28][29][30][31][32] as is necessary for high-efficiency wide-band-gap perovskite solar cells that commonly have both mixed cations and mixed halides. [33][34][35] However, there are many remaining challenges: these perovskite compositions require four or more precursor sources, creating a complex processing space; evaporation tools require high capital expenses and have not successfully been introduced to the photovoltaics market at scale; and vacuum-deposited perovskites have not yet achieved the same cell efficiencies as their solution-processed counterparts.…”

Constructing Hybrid Semiconductor Thin‐Films for Advanced Photovoltaics

“…[176] Organo-halide perovskites are generally prepared in a high vacuum chamber, utilizing three different thermal sources, each source is equipped with a crucible and a quartz crystal microbalance (QCM) sensor, as illustrated in Figure 9. [177] The thickness and deposition rate of the layers are monitored using the quartz oscillator microbalances. Experiments utilizing the vacuum deposition method maintain precursor stoichiometry during deposition, and an annealing step is not required to fully convert the as-deposited films into the perovskite structure.…”