CH₃NH₃PbI₃ and HC(NH₂)₂PbI₃ Powders Synthesized from Low‐Grade PbI₂: Single Precursor for High‐Efficiency Perovskite Solar Cells

Abstract

High-efficiency perovskite solar cells are generally fabricated by using highly pure (>99.99 %) PbI mixed with an organic iodide in polar aprotic solvents. However, the use of such an expensive chemical may impede progress toward large-scale industrial applications. Here, we report on the synthesis of perovskite powders by using inexpensive low-grade (99 %) PbI and on the photovoltaic performance of perovskite solar cells prepared from a powder-based single precursor. Pure APbI [A=methylammonium (MA) or formamidinium (FA)] perovskite powders were synthesized by treating low-grade PbI with MAI or FAI in acetonitrile at ambient temperature. The structural phase purity was confirmed by X-ray diffraction. The solar cell with a MAPbI film prepared from the synthesized perovskite powder demonstrated a power conversion efficiency (PCE) of 17.14 %, which is higher than the PCE of MAPbI films prepared by using both MAI and PbI as precursors (PCE=13.09 % for 99 % pure PbI and PCE=16.39 % for 99.9985 % pure PbI ). The synthesized powder showed better absorption and photoluminescence, which were responsible for the better photovoltaic performance. For the FAPbI powder, a solution with a yellow non-perovskite δ-FAPbI powder synthesized at room temperature was found to lead to a black perovskite film, whereas a solution with the black perovskite α-FAPbI powder synthesized at 150 °C was not transformed into a black perovskite film. The α↔δ transition between the powder and film was assumed to correlate with the difference in the iodoplumbates in the powder-dissolved solution. An average PCE of 17.21 % along with a smaller hysteresis [ΔPCE=PCE -PCE )=1.53 %] was demonstrated from the perovskite solar cell prepared by using δ-FAPbI powder; this PCE is higher than the average PCE of 17.05 % with a larger hysteresis (ΔPCE=2.71 %) for a device based on a conventional precursor solution dissolving MAI with high-purity PbI . The smaller hysteresis was indicative of fewer defects in the resulting FAPbI film prepared by using the δ-FAPbI powder.

A Compact and Smooth CH3NH3PbI3 Film: Investigation of Solvent Sorts and Concentrations of CH3NH3I towards Highly Efficient Perovskite Solar Cells

“…The presence of the pinholes may result in subsequently coated HTM solutions to deleteriously infiltrate into the perovskite absorber layer. It increased the recombination of electron and hole due to the large contact area between HTM and perovskite [ 13 ]. Furthermore, for NAA and NHA solvents, some nanorods/nanoplates were observed to grow on the film surface, which will be detrimental to the performance of the perovskite solar cell.…”

“…Organic-inorganic lead halide perovskite solar cells have attracted intensive attention due to the remarkable progress in power conversion efficiency (PCE), increasing rapidly to over 22% in a few years [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. The PCEs of perovskite solar cells with various architectures (mesoporous or planar heterojunction structures) are strongly dependent on the morphology of the perovskite film [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”

Substance and shadow of formamidinium lead triiodide based solar cells

“…To overcome such challenges, application of pre-synthesized halide perovskite powder as precursor is emerging recently which scores with its higher reproducibility and adaptability of both wet-and dryprocessibility. [82][83][84] Similar to the field of ceramics and metals [85] ; various techniques such as mechanochemical, precipitation, and sonochemical processes can be utilised for the powder synthesis. -FAPbI3 powder was synthesized through a roomtemperature precipitation technique and the PSCs gave higher reproducibility and low trap density along with the improved efficiency was shown as compared to the conventional route.…”

Recent Advances and Perspectives on Powder‐Based Halide Perovskite Film Processing

“…[124] This is supported by the findings of Zhang et al, who showed that even when using low-grade PbI 2 precursors, precipitated FAPbI 3 or MAPbI 3 powder exhibits a high purity due to a self-cleaning effect in the course of the precipitation process. [41,129] Dou et al investigated the degradation of conventional precursor solutions of triple cation mixed perovskites in DMF, identifying a hydrolysis of DMF with trace water in the solution, thereby forming formic acid (HCOOH) and dimethylamine (DMA). [29] The latter impedes the subsequent crystallization of the perovskite and also leads to a faster degradation of both, thin films and solar cells that were processed from these solutions.…”