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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - APOLO (SmArt Designed Full Printed Flexible RObust Efficient Organic HaLide PerOvskite solar cells)

Teaser

Summary

Conventional PV modules are limited in their design and have not been exploited fully in potential markets as buildings, textiles, automotive. Perovskite PV technology has an enormous potential to meet these needs without sacrificing high efficiency. The current main challenges of the technology lie in short lifetime, moderate efficiency with flexible substrates and higher production cost of high efficiency devices relative to the market-dominant silicon PV. APOLO aims to surpass the aforementioned barriers for market deployment by the development of stable and reproducible high-efficient Perovskite Solar Cells (PSCs) using scalable and low-cost processes and reducing the amount of toxic materials in combination with flexibility. The project envisages the following advances:
1. Advancement of flexible PSC with high efficiency (22%) by the development of advanced materials and the implementation of light management structures and antisoiling strategies.
2. Development of long-life time flexible PSCs and modules through advanced transporting layers and smart encapsulation with at least 90% of initial efficiency after 1000h under accelerated ageing and keeping at least 90% of flexibility.
3. Development of sustainable and scalable printing process for flexible PSCs and modules using innovative solvent engineering and low temperature (below 150oC) processing. End of life of final product will be also consider with the design and development of a complete recycling process that will guarantee the selective isolation of lead after PSC life.
4. Development of a PSC integrated prototype for Building Integrated PV application.

Work performed

APOLO started with defining the baseline for PSC cells and modules, as a reference for comparison with the new developments of the project. In WP2, dedicated to advanced materials, partners carried out interfacial layer engineering of PSCs. EPFL synthesized new hole-transporting materials (HTMs) and tested the materials by fabrication of PSCs. UNITOV and Fraunhofer worked on optimization of electron-transporting layers (ETLs) for low-temperature processed PSCs on both rigid and flexible substrates. ARK and CEA developed new liquid encapsulant (LE) formulation adapted to APOLO flexible cells and modules to protect encapsulated devices from moisture. LEITAT developed several formulations for the antisoiling coatings based on fluoroalkylsilanes precursor to reduce the soiling deposition on the surface of the devices. In WP3 UNINOVA modelled and optimised light trapping (LT) structures to be integrated in the PSCs. The effects demonstrated the means to reduce the thickness of the perovskite absorber improving flexibility. UNITOV and Fraunhofer performed the electrical modelling and simulations of PSCs to optimise the module architecture and to provide models of the effects if ions in the PSCsâ€™ response. CEA developed a model for designing a module architecture that tightly encapsulates the cell layers. WP4 aims to up-scale APOLO devices on flexible substrates to large areas, focusing in low temperature manufacturing processes for the active layers, mainly ETL, solvent engineering for the perovskite precursors solution to avoid toxic and hazardous solvents and soft-lithography for LT microstructures. In WP5, on stability and recycling process, partners tested 3 type of encapsulation strategies with flexible and rigid cells. The ageing tests started with preliminary testing and long-term aging. AC did theoretical calculation and experiments with components and devices provided by the partners for recycling process. Standardization, technical, social and environmental assessments in WP6 provide key information about the technology to better achieve industrialization and understand if APOLO devices will be economically competitive and have a predominant role on the market. Critical aspect related to PV regulations and standardization are evaluated and defined. Aging protocols related to life time definition and environmental regulation and recycling have been preliminary analysed. First steps for LCA/LCC analysis has been done.

Final results

APOLO achieves PSCs with up to 20,79% efficiency on small area rigid devices by the introduction of a 2D perovskite (2DP) layer developed by EPFL as passivation strategy. The 2DP layer has been proved also as HTL material as replacement of Spiro-OMeTAD. The PSCs with the 2DP HTL showed a significantly improved stability during operation under constant illumination, maintaining 70% of the initial PCE until 265h while the device without the 2DP HTL lasted less than 5h. HTMs have been synthetized with benzodipyrrole as core unit. Devices fabricate using the HTMs with fluorinated untional group showed the best PCE after reference devices using Spiro. The efforts in optimisation of the printing processing of PSCs led to >15% stabilized PCE on mesostructured n-i-p cells on glass substrates and up to 15% PCE on smalls cells on flexible PET using SnO2 deposited by automated spray coating process. 20% PCE on planar n-i-p mini-modules on glass was achieved using low temperature processing, the highest efficiency recorded so far for perovskite-based devices. 4 green solvents have been demonstrated to successfully dissolve PbI2 using 10-20 vol% of DMSO; APOLO also proved ternary mixtures of (additive/DMSO/green solvent) to effectively dissolve PbI2 at high concentrations. All the processes in the different layers of flexible PSCs use temperatures below 150oC. Optoelectronic simulations of the incorporation of LT structures to PSC were developed to provide theoretical guidelines for the experimental fabrication activities. They showed that 22.8% photocurrent enhancement can be expected with a superstrate PSC configuration compatible only with transparent substrates and 24.4% photocurrent enhancement with substrate-type PSC configuration compatible with opaque substrates as metal sheets. The effects demonstrated show the means to reduce the physical thickness of the perovskite absorber towards a thinner layer (300 nm) with higher optical density, thus yielding improved photocurrent, hence efficiency, together with potential for higher mechanical flexibility. Partners have developed innovative colloidal lithography processes for precise engineering of photonic structures onto flexible PET substrates. Antisoiling coatings based on fluoroalkilsilanes have shown similar hydrophobicity (90-107Â° water contact angles) and higher oleophobicity (water contact angles around 90o) than commercial coatings when deposited in the barrier films used in the encapsulation of APOLO devices. The soil deposition over the barrier films coated films fluoroalkyl-based solutions is lower than in the pristine barrier films, indicating a possible enhancement in the energy production. The Water Vapour Transmission Rate (WVTR) of nanocompoused LE is around 2,7 g.mm.m-2.d-1. APOLOâ€™s objective is challenging but we already achieved performances close to the benchmark. Initial stability tests have started to include stability as criteria for the material and processing selection. The damp heat aging (85Â°C/85%RH) of rigid and flexible cells were compared with 2 types of encapsulation with glass. It was demonstrated that the edge width is a crucial parameter regarding the encapsulation layout. With the large design and glass encapsulation, the T90 (10% of losses in efficiency) of the flexible cells is in 800h.