A large area and highly stable perovskite solar module (10 cm × 10 cm, active area ∼70 cm2) is demonstrated using low cost processing methods and materials.

Hybrid perovskites are recently developed photoactive semiconductors that hold great promise for next-generation solar cells, with devices incorporating them reaching certified efficiencies as high as 22.1%. [1] This high performance is coupled with a relative low cost, as perovskites comprise earth-abundant elements that are amenable to deposition from the solution-state by scalable, inexpensive printing processes. [2] Recent work has focused on improving their long-term stability with significant progress being reported in encapsulation techniques and scalability with the production of modulescale devices (100 cm 2 ) exhibiting efficiencies of over 11%. [3][4][5][6] These developments have resulted in efforts to commercialize perovskite solar cells; however, there is still concern over the potential to achieve the 25-year service lifetimes necessary to make perovskites a disruptive technology.Photoactive perovskite semiconductors are highly tunable, with numerous inorganic and organic cations readily incorporated to modify optoelectronic properties. However, despite the importance of device reliability and long service lifetimes, the effects of various cations on the mechanical properties of perovskites are largely overlooked. In this study, the cohesion energy of perovskites containing various cation combinations of methylammonium, formamidinium, cesium, butylammonium, and 5-aminovaleric acid is reported. A trade-off is observed between the mechanical integrity and the efficiency of perovskite devices. High efficiency devices exhibit decreased cohesion, which is attributed to reduced grain sizes with the inclusion of additional cations and PbI 2 additives. Microindentation hardness testing is performed to estimate the fracture toughness of single-crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. The devices found to have the highest fracture energies are perovskites infiltrated into a porous TiO 2 /ZrO 2 /C triple layer, which provide extrinsic reinforcement and shielding for enhanced mechanical and chemical stability. Perovskite Solar CellsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

A fully printable, hole‐conductor‐free perovskite solar cell with a simple and low‐cost fabrication route and high stability is well placed for commercialization. We aim to simplify the fabrication process of these solar cells by replacing the mesoporous TiO2 (meso‐TiO2) layer with a thick ZrO2 layer. This new architecture required only three steps: screen‐printing first the compact TiO2 (c‐TiO2), second the mesoporous ZrO2 layer (for perovskite infiltration), and third the carbon electrode. To improve the solar cell performance of the architecture, the c‐TiO2 and ZrO2 printing process are optimized. After systematic optimization of these processes, we found that the double‐printing of the c‐TiO2 layer and an increase of the ZrO2 later thickness from 1.4 to 2.1 μm in the device structure gives an optimized efficiency of 9.69 %, which is comparable to that of standard carbon devices with meso‐TiO2. This method provides an approach to reduce the fabrication time and thermal budget for fully printable solar cells.

Excess lead iodide (PbI2) has been reported to improve the power conversion efficiency (PCE) in the standard perovskite solar cell (PSC) with 2,2,7,7‐Tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9‐ spirobifluorene (spiro‐OMeTAD) as a hole‐transporting material. In this study, we studied the effect of having excess PbI2 in fully printable carbon‐based perovskite solar cells (PSC). Excess amounts of PbI2, ranging from 0 % to 15 %, were added to the equimolar perovskite solution for infiltration in the carbon‐based PSC architecture. There was an improvement in the average value of open‐circuit voltage (0.87 to 0.91 V) with increased PbI2, but there was no clear trend in fill factor and current density. All devices showed good stability under ambient conditions without encapsulation. The device containing 15 % excess PbI2 showed degradation under continuous illumination, whereas there was no degradation with an equimolar ratio of perovskite precursors.

Altering cation and anion ratios in perovskites has proven an excellent means of tuning the perovskite properties and enhancing the performance. Recently, methylammonium/formamidinium/cesium triple‐cation mixed‐halide perovskites have demonstrated efficiencies up to 22 %. Similar to the widely explored methylammonium lead halide, excess PbI2 is added to these perovskite films to enhance their performances. The excess PbI2 is known to be beneficial for the performance. However, its impact on stability is less well known. Triple‐cation perovskites deploy excess PbI2 up to 8 %. Thus, it is imperative to analyze the role of excess PbI2 in the degradation kinetics. In this study, the amount of PbI2 in the triple‐cation perovskite films is varied and the degradation kinetics monitored by X‐ray diffraction and optical absorption spectroscopy. The inclusion of excess PbI2 is shown to adversely affect the stability of the material. Faster degradation kinetics are observed for samples with higher PbI2 contents. However, samples with excess PbI2 also showed superior properties such as enhanced grain sizes and better optical absorption. Thus, careful management of the PbI2 quantity is required to obtain better stability and alternative pathways should be explored to achieve better device performance rather than adding excess PbI2.

Additives are frequently used to enhance material properties. The addition of the processing additive 5‐aminovaleric acid iodide (5‐AVAI) into printed mesoscopic perovskite solar cells is shown to have a strong impact on the device performance and stability. Although it is difficult to understand the impact of 5‐AVAI as a processing additive by examining only the final thin films, the evolution of morphology with and without 5‐AVAI reveals that 5‐AVAI influences the crystallization behavior of the perovskite. In situ grazing incidence wide angle X‐ray scattering (GIWAXS) is performed to follow the perovskite formation within the printable all‐porous TiO2/ZrO2/carbon architecture and investigate the influence of 5‐AVAI on the perovskite crystallization within the scaffold. Using such time‐resolved measurements, the suppression of large crystalline perovskite grains is identified early in the fabrication process when 5‐AVAI is present, resulting in improved material backfilling. These observations highlight the importance of 5‐AVAI in the precursor solution for reliable fabrication of printed perovskite solar cells relying on the infiltration of a scaffold structure.

We present the fabrication of highly efficient large-area carbonbased perovskite solar cells (C-PSCs) using CsX (X = Cl, Br, and I)-modified mesoporous (mp) TiO 2 beads of 40 nm size as an electron transport material. Here, triple-layered scaffolds made of cesium halide-modified TiO 2 exhibit efficient charge extraction as confirmed by enhanced photoluminescence quenching and inhibit the UV-activated degradation processes of perovskite, leading to an enhanced operational stability. Among the three cesium halide modifications, devices containing CsBr-modified TiO 2 showed the highest short-circuit current density, yielding a photoconversion efficiency (PCE) of 12.59% of the device, with 0.7 cm 2 active area and 11.55% for a large-area module (70 cm 2 ). These devices are stable in an ambient atmosphere (25 °C, 65−70% RH) over 2700 h as well as at a high temperature (85 °C) over 750 h with virtually no hysteresis.

Solution processed thin film organic-inorganic perovskites are key to the large scale manufacturing of next generation wafer scale solar cell devices. The high efficiency of the hybrid perovskite solar cells is derived mainly from the large carrier mobility and the charge dynamics of films, which heavily depend on the type of solvent used for the material preparation. Here, we investigate the nature of conduction and charge carrier dynamics of mixed organic-inorganic cations [methylammonium (MA), formamidinium (FA), and cesium (Cs)] along with the mixed halides [iodine (I) and bromine (Br)] perovskite material [Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 ] synthesized in different solvents using optical pump terahertz probe (OPTP) spectroscopy. Our findings reveal that carrier mobilities and diffusion lengths strongly depend on the type of solvent used for the preparation of the mixed cation perovskite film. The mixed cation perovskite film prepared using dimethylformamide/dimethylsulfoxide solvent shows greater mobility and diffusion length compared to γ-butyrolactone solvent. Our findings provide valuable insights to improve the charge carrier transport in mixed cation perovskites through solvent engineering.