Thermally evaporated methylammonium-free perovskite solar cells

Ji, Ran; Zhang, Zongbao; Cho, Changsoon; An, Qingzhi; Paulus, Fabian; Kroll, Martin H.; Löffler, Markus; Nehm, Frederik; Rellinghaus, Bernd; Leo, Karl; Vaynzof, Yana

doi:10.1039/d0tc01550d

Cited by 52 publications

(78 citation statements)

References 44 publications

(51 reference statements)

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“…Remarkably, MA based perovskites such as methylammonium lead triiodide (MAPbI 3 ) [68,69] or methylammonium tin triiodide (MASnI 3 ) [70,71] show the biggest difference in the grain size, with solutionprocessing leading to grains on the order of micrometers or even tens of micrometers, while thermally evaporated films exhibit grains of ≈100 nm. Mixed cation compositions, such as the triple cation (CsMAFA) [72,73] and the MA-free alternative (CsFA), [21,34] show far smaller grain sizes (100-200 nm) when deposited from solution, making the microstructure more similar to that achieved by thermal evaporation.…”

Section: Controlling the Perovskite Layer Microstructurementioning

confidence: 99%

“…Adapted with permission. [21] Copyright 2020, RSC Publishing, [34] Copyright 2018, AAAS, [68] Copyright 2020, Elsevier, [69] Copyright 2017, RSC Publishing, [70] Copyright 2016, RSC Publishing, [71] Copyright, 2015, American Chemical Society, [72] Copyright 2018, Wiley-VCH, [73] Copyright 2016, RSC Publishing.…”

Section: Controlling the Perovskite Layer Microstructurementioning

confidence: 99%

“…Roughly 30% of reports show the presence of hysteresis, which in some cases is very significant. [21,74,116] These results highlight that the issue of hysteresis in thermally evaporated perovskite solar cells is not adequately addressed, requiring the development of new strategies to suppress it.…”

Section: Photovoltaic Performancementioning

confidence: 99%

“…Several reports investigated the thermal evaporation of more complex perovskite compositions, such as double [ 99 ] or triple cation, [ 72 ] or more recently the emerging MA‐free perovskites, such as FAPbI 3 [ 100 ] or (Cs,FA)Pb(I,Br) 3 compositions. [ 21,22 ] The efficiency of these devices is <19%, which could originate from various factors. As described earlier, the microstructure of thermally evaporated layers typically consists of smaller, less regular grains, resulting in more grain boundaries and potentially, higher recombination losses.…”

Section: Photovoltaic Performancementioning

confidence: 99%

“…Importantly, unlike solution‐processed perovskite films, it is possible to form crystalline perovskite layers by thermal evaporation without annealing; [ 20 ] however, many studies still rely on annealing for improving the evaporated films’ properties. [ 21,22 ]…”

Section: Introductionmentioning

confidence: 99%

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The Future of Perovskite Photovoltaics—Thermal Evaporation or Solution Processing?

Vaynzof

2020

Advanced Energy Materials

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162

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single solution, which is deposited onto the substrate, following by a thermal annealing step. [6,7] While this approach is very simple and is still relatively common for certain perovskite compositions, [8,9] the perovskite precursors maybe undergo various chemical reactions in solution, which will influence both the resulting film and the performance of photovoltaic devices. [10] An alternative approach, especially popular in the early days of perovskite research, is the two-step approach, in which one of the precursors is deposited first, followed by the deposition of a second precursor and thermal annealing. [11] Most commonly, the first precursor (e.g., lead iodide, PbI 2) is deposited by spin-coating, while the second one (e.g., methylammonium iodide, MAI) can be deposited by dipping the sample into a solution, [12] or by spin-coating on top of the first layer. [13] For a time, devices fabricated using the two-step method showed higher performance than those made using the one-step, [14] but the situation drastically changed upon the introduction of the solvent engineering approach, [15] which remains the most commonly used to date. This method is a modification of the one-step approach, with all perovskite precursors deposited in a single step, during which an antisolvent is applied triggering the crystallization of the perovskite film. [16] Similarly, several variations of deposition of perovskite layers by thermal evaporation have also been demonstrated. These include the single-source evaporation, sequential evaporation and multiple source coevaporation (Figure 1). Single-source evaporation is possible either via combining the perovskite precursors into a single crucible [17] or by first preparing (e.g., via solution-processing) perovskite crystals that are ground into a powder for evaporation. [18] Sequential evaporation follows a similar approach to that of the two-step solution-processed deposition, with each precursor evaporated separately, following by a thermal or vapor annealing. [19] The most common approach, however, is based on the multisource evaporation, in which each precursor is loaded into a separate crucible and is coevaporated along with all other precursors to form the perovskite layer. Importantly, unlike solution-processed perovskite films, it is possible to form crystalline perovskite layers by thermal evaporation without annealing; [20] however, many studies still rely on annealing for improving the evaporated films' properties. [21,22] It is noteworthy that many additional methods for the deposition of perovskite films exist such as inkjet printing, [23] spray coating, [24] chemical vapor deposition, [25] flash evaporation, [26] and many others; [27] however, these methods are less common in literature and generally show lower performance than those fabricated by the methods outlined above. The last decade has seen remarkable advancements in the field of perovskite materials and photovoltaic technologies. One of their most extraordinary characteristics is the high quality of layer...

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Section: Controlling the Perovskite Layer Microstructurementioning

confidence: 99%

Section: Controlling the Perovskite Layer Microstructurementioning

confidence: 99%

Section: Photovoltaic Performancementioning

confidence: 99%

Section: Photovoltaic Performancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The Future of Perovskite Photovoltaics—Thermal Evaporation or Solution Processing?

Vaynzof

2020

Advanced Energy Materials

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162

148

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From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

Abzieher

Feeney

Schackmar

et al. 2021

Adv Funct Materials

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Vacuum-based deposition of optoelectronic thin films has a long-standing history. However, in the field of perovskite-based photovoltaics, these techniques are still not as advanced as their solution-based counterparts. Although high-efficiency vacuum-based perovskite solar cells reaching power conversion efficiencies (PCEs) above 20% are reported, the number of studies on the underlying physical and chemical mechanism of the co-evaporation of lead iodide and methylammonium iodide is low. In this study, the impact of one of the most crucial process parameters in vacuum processes-the substrate material-is studied. It is shown that not only the morphology of the co-evaporated perovskite thin films is significantly influenced by the surface polarity of the substrate material, but also the incorporation of the organic compound into the perovskite framework. Based on these studies, a selection guide for suitable substrate materials for efficient co-evaporated perovskite thin films is derived. This selection guide points out that the organic vacuum-processable hole transport material 2,2″,7,7″-tet ra(N,N-di-p-tolyl)amino-9,9-spirobifluorene is an ideal candidate for the fabrication of efficient all-evaporated perovskite solar cells, demonstrating PCEs above 19%. Furthermore, building on the insights into the formation of the perovskite thin films on different substrate materials, a basic crystallization model for co-evaporated perovskite thin films is suggested.

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From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

Abzieher¹,

Feeney²,

Schackmar³

et al. 2022

Adv Funct Materials

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The originally published article contains an error in the calculation of the mean free path of methylammonium iodine (MAI) according to equation (2) in the main manuscript (wrong diameter for the MAI molecule), which also resulted in too low values for the mean free path of MAI in Figure 1b and a wrong explanation in the introductory part of the manuscript in section 2.1.The corrected Figure 1b is as follows:Relating to this change, a short paragraph starting on page 4 in the main manuscript, left column second-to-last line ("Due to the larger diameter of the MAI molecule compared to PbI 2 […] resulting in a loss of the directed effusive flux and a transition to a more CVD-like evaporation behavior.") is not completely correct. The mean free paths of MAI and PbI 2 are rather similar after correction. Therefore, the conclusion that the loss in the effusive component of the MAI evaporation is due to the increased number of collisions between MAI molecules is unlikely. However, the clear indications that the MAI evaporation in the employed process is not fully effusive, but at least in part of CVD-like nature (e.g., the high background pressure and the conversion of a PbI 2 film in presence of the background MAI atmosphere as discussed in the supporting information) remains valid, but must have another primary cause. As mentioned in the original manuscript and shown by others, the decomposition of MAI into more volatile compounds is expected to be one reason for the strong rise in background pressure as well as the CVD-like evaporation characteristic. Given the fact that a strong CVD-like evaporation characteristic of MAI is observed in our process, the description of the employed process as well as its challenges are still valid in the original manuscript. Most importantly, the influence of the substrate material (here polarity) on the film formation is not influenced by this initially wrong interpretation of our process since the substrate dependency is linked to the interaction of the substrate surface and the condensing molecules in this complex mixed process environment as shown throughout the manuscript.

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Thermally evaporated methylammonium-free perovskite solar cells

Abstract: Efficient thermally evaporated MA-free perovskite solar cells are developed by optimising their stoichiometry and annealing procedures.

Cited by 52 publications

References 44 publications

The Future of Perovskite Photovoltaics—Thermal Evaporation or Solution Processing?

The Future of Perovskite Photovoltaics—Thermal Evaporation or Solution Processing?

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

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