The commercial manufacturing of perovskite solar modules (PSM) suffers from stability concerns and scalability issues. We demonstrate a hole-conductor-free printable solar module embodiment, which employs a triple layer of mesoporous TiO2/ZrO2/carbon as scaffold, and is infiltrated by a mixed cation lead halide perovskite (5-AVA)x(MA)1−xPbI3 as a light harvester. Here, hole conductor or Au reflector are not employed, and instead, the back contact comprises simply a printed carbon layer. Upon optimizing the thickness alignment of the triple mesoscopic layer and the design of the active area, the unit cell shows 14.02% power conversion efficiency (PCE) under 100 mW cm−2 condition, while a larger area of 10 serially connected cells module (10 × 10 cm2), shows a 10.4% PCE on an active area of 49 cm2. Light-soaking stability of 1000 h has been demonstrated, as well as local outdoor stability of 1 month and a shelf-life stability of over 1 year. This paves the way for the realization of efficient and stable large-area PSMs for industrial deployment.

Stable Large-Area (10 × 10 cm2) Printable Mesoscopic Perovskite Module Exceeding 10% Efficiency

Hybrid organic-inorganic perovskite photovoltaics (PSCs) have attracted significant attention during the past decade. Despite the stellar rise of laboratory-scale PSC devices, which have reached a certified efficiency over 25% to date, there is still a large efficiency gap when transiting from small-area devices to large-area solar modules. Efficiency losses would inevitably arise from the great challenges of homogeneous coating of large-area high quality perovskite films. To address this problem, we provide an in-depth understanding of the perovskite nucleation and crystal growth kinetics, including the LaMer and Ostwald ripening models, which advises us that fast nucleation and slow crystallization are essential factors in forming high-quality perovskite films. Based on these cognitions, a variety of thin film engineering approaches will be introduced, including the anti-solvent, gas-assisted and solvent annealing treatments, Lewis acid-base adduct incorporation, etc., which are able to regulate the nucleation and crystallization steps. Upscaling the photovoltaic devices is the following step. We summarize the currently developed scalable deposition technologies, including spray coating, slot-die coating, doctor blading, inkjet printing and vapour-assisted deposition. These are more appealing approaches for scalable fabrication of perovskite films than the spin coating method, in terms of lower material/solution waste, more homogeneous thin film coating over a large area, and better morphological control of the film. The working principles of these techniques will be provided, which direct us that the physical properties of the precursor solutions and surface characteristics/temperature of the substrate are both dominating factors influencing the film morphology. Optimization of the perovskite crystallization and film formation process will be subsequently summarized from these aspects. Additionally, we also highlight the significance of perovskite stability, as it is the last puzzle to realize the practical applications of PSCs. Recent efforts towards improving the stability of PSC devices to environmental factors are discussed in this part. In general, this review, comprising the mechanistic analysis of perovskite film formation, thin film engineering, scalable deposition technologies and device stability, provides a comprehensive overview of the current challenges and opportunities in the field of PSCs, aiming to promote the future development of cost-effective up-scale fabrication of highly efficient and ultra-stable PSCs for practical applications.

Understanding of perovskite crystal growth and film formation in scalable deposition processes

Organic–inorganic halide perovskite solar cells (PSCs) have achieved amazing progress in terms of power conversion efficiency (PCE), rising from 3.8% to over 23.3%. Owing to perovskites’ low nucleation and crystallization activation energy (56.6–97.3 kJ mol−1), a range of low temperature and large-scale solution fabrication processes have been actively investigated for potential commercialization. Although many excellent research institutes and enterprises have emerged to advance commercialization of PSCs, the performance of devices which have large areas still lag much farther behind those of smaller lab scales. The performances of PSCs are predominantly determined by the quality of the perovskite film, which in turn, is controlled by the fabrication process. A comprehensive and in-depth understanding of the nucleation and growth process during perovskite crystallization is imperative for the further advancement of large-scale manufacturing of high quality perovskite films. This review summarizes recent advances in the commercialization of the PSCs market, and critically reviews promising large-scale solution manufacturing methods combined with their physical properties and relevant challenges with the crystallization thermodynamics and kinetics of perovskites. The hurdles and challenges of commercialization and possible approaches and solutions are discussed.

From scalable solution fabrication of perovskite films towards commercialization of solar cells

A Review on Additives for Halide Perovskite Solar Cells

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New Strategies for Defect Passivation in High-Efficiency Perovskite Solar Cells

Carbon based perovskite solar cells are fabricated for the first time in a room temperature environment by employing inkjet infiltration of perovskite precursor ink. The fabricated perovskite solar cells exhibit impressive performance reproducibility with this automated method and exhibit high stability when exposed to 35 degrees C for a period of 1046 hours.

Air Processed Inkjet Infiltrated Carbon Based Printed Perovskite Solar Cells with High Stability and Reproducibility

We report humidity assisted thermal exposure (HTE) as a post-treatment method for carbon based printed perovskite solar cells (CPSCs). The method does not only improve the interfaces of different layers of the printed stack, but also provides a pathway to fabricate high performance CPSCs with low hysteresis along with high stability. The HTE treatment directly influences over the associated components in the stack and remarkably improves each photovoltaic parameter of the CPSCs as seen by several characterization schemes presented in this study. The average initial efficiency (9.0% ± 0.2%) of the CPSCs of a batch was significantly improved to 13.1% ± 0.2% i.e. as high as 45% when subjected to HTE treatment for a period of 200 hours. Furthermore, the highest average efficiency obtained from the same batch from reverse scanning was 13.8% ± 0.4% with a CPSC attaining as high as 14.3% when exposed to the same thermo-humid environment for a period of 115 hours. Above all, the stability of the HTE treated CPSCs was also not compromised for over 350 hours under full-sun illumination stress testing at 40 °C. The results presented in this work provide an opportunity to adopt HTE treatment as a complementary step for the fabrication of high-performance carbon-based perovskite solar cells with low hysteresis accompanied by high durability and performance reproducibility.

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High performance carbon-based printed perovskite solar cells with humidity assisted thermal treatment

Previously, it has been shown that the grain size distribution plays an important role in the mechanical properties of welded steel. In the previous investigation, the volume-weighted average grain size has been shown to capture the influence of grain size distribution, resulting in a better fitting Hall–Petch relationship between grain size and hardness. However, the previous studies exclude the effects arising from local variation in grain size. In this paper, the grain size measurement methods are extended for the characterisation of the local grain size variation, which is significant for welded joints and can have an adverse effect on mechanical properties. The local gradient of grain size variation and its dependency on measurement direction are considered. In addition, examples of grain size and hardness variation are shown for S355 base metal and two weld metals, and characteristic differences are highlighted and discussed. The coarse-grained areas of a heterogeneous microstructure are found to have lower hardness than fine-grained areas. However, the surrounding microstructure, i.e. local grain size gradient, has an influence on the measured hardness values.

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Teemu Sarikka

Papers

Air Processed Inkjet Infiltrated Carbon Based Printed Perovskite Solar Cells with High Stability and Reproducibility

High performance carbon-based printed perovskite solar cells with humidity assisted thermal treatment

Characterisation of local grain size variation of welded structural steel

Characterisation of local grain size variation of welded structural steel.IIW Doc.No IX-2516-15 (IX-L-1137-15)

Microstructural, mechanical, and fracture mechanical characterization of SA 508-Alloy 182 dissimilar metal weld in view of mismatch state