Enhanced Environmental Stability of Planar Heterojunction Perovskite Solar Cells Based on Blade‐Coating

Abstract

that the blade-coating process encourages the formation of self-assembled large perovskite crystalline domains featuring uniform fi lm coverage and signifi cantly improved device ambient stability. In addition, we reveal that this blade-coating process can also be applicable to systems based on using the advanced solvent engineering technique reported for high-performance perovskite (CH 3 NH 3 PbI 3 ) solar cells. [ 35,36 ] Blade-coating is a simple, cost-effi cient, and roll-to-roll compatible process for optoelectronic device fabrication. [ 37,38 ] In the case of perovskites, we fi nd that the formation of large crystalline domains is encouraged by the relatively slow solvent drying process in the uniformly wet fi lm formed immediately after solution blading. It may change the nucleation kinetics of perovskites to ensure self-assembly driven growth. Taking advantage of this process, we have applied blade-coating to the preparation of CH 3 NH 3 PbI 3-x Cl x perovskite fi lms to achieve high quality and moisture/air-resistant fi lms under ambient conditions.To examine the processability of perovskite fi lms in ambient and explore the effect of different coating methods on device performance, we have fabricated perovsktie solar cells using both spin-and blade-coating. The fi lms were annealed at 90 °C in air for 2 h after both coating processes; but in the case of bladecoating, the wet fi lms formed immediately after solution blading were kept at room temperature for 40 min before annealing to wait for the majority of N,N -dimethylformamide (DMF) solvent to be evaporated. The same coating and annealing conditions were used for other perovskite fi lms studied later in this work. The device confi guration and energy band diagram of materials used in this study is shown in Figure 1 . [ 39,40 ] The photoactive perovskite layer was prepared from a precursor solution with 1 wt% of 1,8-diiodooctane (DIO) additive following the reported method. [ 23 ] For comparison, we have also fabricated reference perovskite solar cells under inert environment, a N 2 -fi lled glove box. The best performing reference device shows a PCE of 10.30%, and the detailed photovoltaic properties of the reference perovskite cells are shown in Figure S1 in the Supporting Information. Current densityvoltage ( J -V ) characteristics of perovskite solar cells fabricated with two coating methods in ambient conditions are shown in Figure 2 a, with summarized device performance in Table 1 .Hybrid organic-inorganic halide perovskites have attracted signifi cant attention from both academia and industry due to their unique structural and optoelectronic properties such as high crystallinity, excellent charge carrier mobility, luminescence and energy harvesting characteristics [1][2][3][4][5][6][7][8][9][10][11][12] that led to very rapid progress in perovskite solar cells. [13][14][15][16] However, fabrication of high-performance perovskite solar cells, particularly those based on compact titanium dioxide (TiO 2 ) electron-transporting layers, involves hig...

Research Update: Large-area deposition, coating, printing, and processing techniques for the upscaling of perovskite solar cell technology

“…27 Blade coating was also used to fabricate planar heterojunction PSCs, showing a best PCE of 12.2% and good stability in air. 28 Note that blade coating is a cheap and scalable technique and can be used to deposit not only the perovskite active layer but also HTMs and ETL layers, leading to fully printable devices as demonstrated by Yang et al on both glass and flexible substrates. 29 In order to increase reproducibility and automation of deposition it is possible to use the slot die coating, a technique based on a similar principle, but with the possibility of controlling the amount of ink used more precisely and of obtaining a patterned layout.…”

Critical analysis of stability and performance of organometal halide perovskite solar cells via various fabrication method (Review)

“…As been reported, the doctor blade method that fabricate in ambient air condition with planar structure has benefit in stability and photovoltaic performance of perovskite solar cell [23]. Based on the study, scanning electron microscope (SEM) shows the large domains of crystalline and the thin film formation on film substrate are uniformly covered, as depicted in Fig.3.…”

“…Based on the study, scanning electron microscope (SEM) shows the large domains of crystalline and the thin film formation on film substrate are uniformly covered, as depicted in Fig.3. The light absorption that produced the film prepared by using doctor blade technique proved that the dropping PV performance using spin coating technique in ambient air are related to the perovskite degradation [23]. …”

Transamidation of dimethylformamide during alkylammonium lead triiodide film formation for perovskite solar cells

“…A transition at this temperature can explain why temperatures higher than 90°C, often 100°C, have been preferred for successful annealing of perovskites. [12][13][14]25,[35][36][37][38][39][40] At around 90°C, the DMF complex (D) disappears concomitant with the appearance of perovskite peaks [P, Fig. 5(b)].…”

“…Covalent chemical reactions have already been proposed to be involved in perovskite degradation, but only with respect to reactions with water or oxygen. [12][13][14] When considering the reactivity of many components present in perovskite solar cells, such as TiO 2 , [15][16][17] DMF, 18,19 MAI, 20 PbI 2 , water, 21 or HI, 22 we wondered whether additional covalent chemical reactions might be at work during perovskite formation. We turned to time-of-flight secondary ion mass spectrometry (TOF-SIMS), the chemical microscope, to identify changes in chemical composition of perovskite films.…”