The Future of Photovoltaics: Organic, Perovskites, CIGS, Tandem

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In this presentation I will discuss the multiple ways how monolithic perovskite/silicon can be fabricated, built from textured silicon heterojunction solar cells, with an emphasis on solution of the perovskite top cell. Bulk and contact passivation of the perovskite are instrumental to obtain a high performance, which can be obtained through molecular additive engineering. Combined, this recently led to a certified power conversion efficiency of 33.7% for a monolithic perovskite/silicon tandem solar cell. This will be followed by a discussion about the outdoor performance of such tandems and the need for robust and perovskite-compatible encapsulation to do so. I will then move on to discuss reliability aspects of such tandems under accelerated degradation tests such as damp-heat testing, reverse-bias and potential induced degradation, as well as possible mechanical failure due to top-contact delamination. I will conclude my talk with arguing how bifacial perovskite/silicon tandems aid in improved performance as well as stability.

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For the consolidation of organic photovoltaics (OPV), it is crucial to create market pull through the identification and target of strategic niches, where this technology can exploit its fundamental differentiators.1 For instance, materials engineering has enabled wavelength-selective harvesting with transparent OPV for power-generating windows2 and building-integrated photovoltaics.3 Therein, a simultaneous high efficiency and high transparency are needed. While the community has made relevant developments to maximize the optoelectronic properties of OPV devices, little attention has been paid to their structural properties. High-volume manufacturing technologies such as plastic thermoforming and injection moulding can help expand the opportunities, the capabilities, and the seamless integration of OPV.

In this work we demonstrate, for the first time, the feasibility of fabricating OPV cells and modules embedded into structural plastic parts through injection moulding. This process yields lightweight OPV devices with enhanced device robustness and durability, thanks to the hermetical and conformable encapsulation resulting from the plastic injection. We discuss the interplay between the plastic processing conditions and the OPV device performance and stability, as well as highlight relevant optomechanical and physico-chemical material properties, including recyclable thermoplastic polymeric materials that might facilitate material reuse. Finally, we also show how plastic processing can be used to fabricate low-cost, three‑level hierarchically organized micro/nanometric surface textures that provide additional functionalities, such as light management or self-cleaning.4

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An early-stage startup company aiming to supply material and equipment for perovskite-based solar technology with production facilities in Colorado. We are driven by a passion for scientific innovation and a commitment to making a positive impact on the world. Our journey began with a simple but powerful idea: to harness the potential of perovskite materials, accelerate the manufacturing of solar cell semiconductors, and create a diversified and inclusive future workforce.

What is a perovskite solar cell?

Perovskite solar cells (PSCs) were developed about 15 years ago and can achieve higher power conversion efficiencies at lower cost compared to traditional solar cells.

What is the hole transport layer?

Hole transport layers (HTLs) are thin films placed in perovskite solar cells to facilitate the efficient movement of positive charges (holes) from the light-absorbing perovskite layer to the electrode.
Why polymer hole transport materials?

AP's polymer hole transport materials (PHTMs) offer advantages such as high hole mobility, thermal and chemical stability, excellent surface contact and passivation, and cost competitiveness, making them desirable for use as HTLs in perovskite solar cells to enhance their performance and stability.

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Organic photovoltaics (OPVs) are an emerging thin film solar technology based on organic semiconductors. OPVs are promising due to their potential for solution processability, low temperature manufacture, and tuneable absorption. The latter of these allows for semi-transparent OPVs (STOPVs), meaning visible light can be transmitted whilst electricity is still generated. STOPVs have huge potential for building integrated PV, power generating windows, and other architectural and industrial applications.

Here we will discuss our project based on scalable STOPVs, as part of a collaboration between the University of Manchester and Manchester based company Contra Vision. Work so far includes preliminary transfer-matrix modelling work evaluating different active layer components and top electrodes; dilute donor compositions for tuning light utilisation efficiency; and exploration of a variety of charge transport layers towards a fully printed OPV stack.

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Organic photovoltaic technologies are a 3rd generation solar technology which has been steadily improving in the past decade due to rapid evolutions in materials design, device stacks and processing strategies. Due to their high efficiency, non-toxic nature and low-cost-high-volume manufacturing potential, several market-ready applications are now emerging for this technology. For instance, photovoltaic modules for indoor energy harvesting, for integration into buildings such as greenhouses, office buildings or even vehicles. In this presentation Brilliant Matters will outline some of the current challenges in the field of high performance and scalable OPVs from a materials chemistry perspective and will discuss novel materials systems for efficient, stable and scalable OPV devices

In the field of solar energy, it has become a common belief that perovskite solar cells
are advancing at an unprecedented pace. While the historical trajectory may seem
astonishing, we can gain insight by examining the development path of the solar cell
industry, which has progressed from silicon and CIGS (copper indium gallium
selenide) to organic solar cells. Perovskite solar cells represent the culmination of
decades of knowledge and research.
A perovskite solar cell is composed of multiple layers. Each layer is carefully
deposited on a substrate, which imposes certain limitations on the choice of
materials and manufacturing processes for the top layer. To overcome these
limitations, various process technologies such as slot-die coating, blade-coating, and
spray deposition have been developed and refined for large-scale production.
Additionally, a wide range of materials has been extensively studied.
In the presentation, we will delve into the critical considerations for selecting
materials and processes when fabricating perovskite solar cells. Furthermore, we will
highlight the challenges and obstacles associated with these technologies.

Inexpensive metal Al is scarcely utilized as the cathode in the perovskite solar cells (PVSCs) because its violent reaction with perovskite active layer results in poor device stability in air. A novel solution-processed cathode interlayer material, surfactant encapsulated polyoxometalate complex [(C8H17)4N]4[SiW12O40] (TOASiW12) is employed to modify Al as the cathode. The power conversion efficiency (PCE) of 20.64% has been achieved in the inverted PVSCs. The findings demonstrate that a thin TOASiW12 layer can effectively obstruct the chemical reaction between Al and perovskite layer, and significantly enhance the device stability. The unencapsulated devices with TOASiW12-modified Al retain more than 80% of the initial PCE after 350 h storage in the ambient atmosphere at 45% relative humidity. This work provides an alternative cathode interlayer material for efficient and stable inverted PVSCs.

We have provided analytical services and R&D support to customers using innovative analytical techniques and physical analyses for over 40 years, and we have been involved in Perovskite Solar Cells for over 10 years. We will introduce the latest analytical technologies for Perovskite Solar Cells, for example, crystal structure evaluation in the cells by XRD and 4D-STEM, electrical characteristics of the power generation layer for the cells by SSRM and SEM, evolved gas analysis during sample heating by TPD-MS, and depth profile analysis of element and organic molecules distribution by SIMS, etc. Please learn more about our technical information at the presentation

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Fabricating devices with non-vacuum roll-to-roll processes that intrinsically host nano-scale pn junctions offer an attractive platform to create low-cost, flexible, lightweight opto-electronic devices. Incumbent 3G nano technologies still face significant challenges in-terms of stability, toxicity, up-scaling and reproducibility to reach the status of the established technology. Here we present an alternate path that integrates new device structure, process and manufacturing. It features a compact, practical, atmospheric process to manufacture high quality, ordered 3D
nanocrystalline pn homojunction (NHJ) device structures. Exemplified here by two Cu-In-Se (CISe) compounds, the method entails single-step electrodeposition of interconnected network of p-CISe and n-CISe nanocrystals to create a depleted NHJ thin film. Extraordinary attributes the CISe NHJs include non-linear emissions, large carrier mobility, low trap-state-density, long carrier lifetime and likely up-conversion. The NHJ film can be inserted between two electrodes to produce an isotropic device, wherein current can flow in either direction to convert light into electricity or applied voltage into light.
Although originally conceived for CISe solar cells, this radical concept could create NHJs with most II-VI or III-V semiconductors for wide spectrum of applications, e.g., PV panels, LEDs, photodetectors, photoelectrodes, laser diodes, displays, MEMS and optical fibers. Importantly, the NHJ structure can be continuously roll-to-roll processed in ambient atmosphere from aqueous solution. Overall, this approach offers a promising low-cost processing platform to create high performance, stable and scalable devices. The NHJs could essentially perform like 2D planar pn
junctions or artificially ordered 3D nano-structures, but without their high cost and fabrication complexities.

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Key considerations for startups working with contract manufacturers and how to get the most out of the relationship to accelerate product development and commercialization. Examples from roll to roll contract coating for perovskite photovoltaic.

Key considerations for startups working with contract manufacturers and how to get the most out of the relationship to accelerate product development and commercialization. Examples from roll to roll contract coating for perovskite photovoltaic.

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Integrating metal halide perovskite top cells with bottom cells formed by crystalline silicon or low band gap perovskites into monolithic tandem devices has recently attracted increased attention due to the high efficiency potential and application relevance of these cell architectures. Here we present our recent results on monolithic tandem combinations of perovskite top-cells with crystalline silicon, and Sn-Pb perovskites as well as tandem relevant aspects of perovskite single junction solar cells.
In 2020, we have shown that self-assembled monolayers (SAM) could be implemented as appropriate hole selective contacts. The implementation of new generation SAM molecules enabled further reduction of non-radiative recombination losses with high open circuit voltages and fill factor. By fine-tuning the SAM molecular structure even further, the photostability of perovskite composition with tandem-ideal band gaps of 1.68 eV could be enhanced by reduction of defect density and fast hole extraction. That enabled a certified efficiency for perovskite/silicon tandems at 29.15%.

By optical optimizations, we could further improve this value to 29.80% in 2021. Periodic nanotextures were used that show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell on top of the nanotexture.

In the end of 2022, we enabled a new world record for perovskite/silicon tandem solar cells at 32.5% efficiency. We demonstrated that an additional surface treatment strongly reduces interface recombination and improves the band alignment with the C60 electron transporting material. With these modifications, single junction solar cells show high open circuit voltages of up to 1.28 V in a p-i-n configuration, and we achieve 2.00 V in monolithic tandem solar cells. A comparable surface treatment was also applied to 1.80 eV band gap perovskites to enable Voc values of 1.35 V and these were integrated into monolithic all-perovskite tandem solar cells enabling a certified efficiency of 27.5%.

In addition to the experimental material and device development, also main scientific and technological challenges and empirical efficiency limits as well as advanced analysis methods will be discussed for perovskite based tandem solar cells. In addition, results on upscaling and stability of these industrial relevant tandem solar cells by thermal evaporation will be shown.

Remarkable progress has been achieved in metal halide perovskite (MHP) photovoltaics after more than a decade of intensive research by thousands of researchers on a handful of lead-based MHP compounds. However, it should be noted that even champion materials are not always thermodynamically stable at room temperature and most alloys suffer from intrinsic photodegradation phenomena. Perhaps for these reasons, the stability of highly performing devices remains marginal and further progress is incrementally made by fine-tuning existing MHP compositions with formulation, passivation, interfacial engineering and processing improvements. MHPs and their alloys are highly diverse materials with a vast chemical parameter space that provides numerous alternative candidates for discovering thermodynamically stable compounds that are likely to be stable under a variety of external stresses. However, it can be daunting to explore this parameter space without a clear framework and the toolkit to translate materials to thin film devices. Existing MHPs have well-tread formulation, passivation and processing pathways that have been hard-won with years of communal learning, whereas new MHP materials require re-learning how to process thin films.

We propose a streamlined approach to material discovery in the context of thin film photovoltaics. First, we have designed a robotic workflow (RoboMapper) that parallelizes and accelerates the screening of materials. In one example, we identify whether a alloys are cubic perovskite, achieve the desired bandgap and are light-stable. We show that RoboMapper reduces time-to-solution of new material candidates by an order of magnitude and commensurately reduces cost, energy and environmental impacts associated with exploring MHP compositional space. Through a physics-based framework linking defects-diffusion-stability, we can further predict which compositions yield light-stable, low-hysteresis and efficient operation in solar cell devices. In a second example we combine RoboMapper workflow with in situ heating of MHP alloys and implement AI identification and classification of phases to automate and accelerate the search for thermally stable perovskite alloys. Finally, with material candidates in hand, we demonstrate the implementation of a self-driving coater (RoboCoater) which autonomously develops and perfects coating recipes for MHP compounds without prior knowledge. Robocoater leverages in-line sensing, ML/AI and decision-making to accelerate 10-100 fold the translation of new materials into thin films and streamlines integration of new materials into device workflows.

Metal halide perovskites are ionic conductors and can undergo oxidation and reduction. Perovskite solar cells often contain metal electrodes that can be oxidized. Redox reactions occur quite rapidly when the cells are operated in reverse bias, which can happen when a shaded cell is forced to match the current of illuminated cells that are connected in series. Shunting typically occurs in reverse bias when silver electrodes are used, but not when transparent conducting oxides or carbon are used. Oxidation of iodide can result in loss of iodine from the perovskite layer, which can also reduce power conversion efficiency. The talk will describe the electrochemical degradation and how feasible it is to protect different types of modules with bypass diodes.