Thin-film Photovoltaic Technologies Research Articles

Development of Lightweight and Flexible Perovskite Solar Cells on Ultrathin Colorless Polyimide Foils.

The development of Perovskite Solar Cells (PSCs) on flexible substrates marks a significant advancement in thin-film photovoltaic technology. However, current state-of-the-art research predominantly utilizes Poly(ethylene terephthalate) (PET) substrate, which limits the deployment to less challenging environments. To address this limitation, we explore the fabrication of inverted PSCs on colorless polyimide (CPI) substrates that can withstand harsh environmental conditions. We employed a sequential sputtering technique to deposit indium tin oxide (bottom electrode) and nickel oxide (hole transport layer) as a base stack for the perovskite. This base layer was further enhanced by incorporating MeO-2PACz into the hole transport bilayer, significantly improving the NiOx interface, and thereby enhancing the efficiency of the devices. The PSCs fabricated on CPI demonstrated a power conversion efficiency (PCE) of 15.52% and a remarkable power-to-weight ratio (PWR) of 4.39 W/g, which is five times higher than that of devices on PET (0.87 W/g). Moreover, the active stack developed in this study can be used on any transparent substrate, showing its broader application potential.

Effective Non-Radiative Interfacial Recombination Suppression Scenario Using Air Annealing for Antimony Triselenide Thin-Film Solar Cells.

Antimony triselenide (Sb2Se3) has become a very promising candidate for next-generation thin-film solar cells due to the merits of their low-cost, low-toxic and excellent optoelectronic properties. Despite Sb2Se3 thin-film photovoltaic technology having undergone rapid development over the past few years, insufficient doping concentration and severe recombination have been the most challenging limitations hindering further breakthroughs for the Sb2Se3 solar cells. Post-annealing treatment of the Sb2Se3/CdS heterojunction was demonstrated to be very helpful in improving the device performance previously. In this work, post-annealing treatments were applied to the Sb2Se3/CdS heterojunction under a vacuum and in the air, respectively. It was found that compared to the vacuum annealing scenario, the air-annealed device presented notable enhancements in open-circuit voltage. Ultimately a competitive power conversion efficiency of 7.62% was achieved for the champion device via air annealing. Key photovoltaic parameters of the Sb2Se3 solar cells were measured and the effects of post-annealing treatments using different scenarios on the devices were discussed.

Ambient-atmosphere fabricated perovskite solar cells with formamidinium iodide passivation for enhanced light absorption

The exceptional photoelectric characteristics and high conversion efficiency have positioned metal halide perovskite as a significant breakthrough in recent thin-film photovoltaic technology. Despite these advantages, perovskite crystalline lattices often contain defects like interstitials, vacancies, and impurities at grain boundaries and surfaces, along with dangling bonds, contributing to the nonradiative recombination processes among photocarriers, which hamper device performance and stability. In this context, we present a simple method to mitigate electronic defects occurring at the interface between perovskite (Cs0.17FA0.83Pb(I0.83Br0.17)3 films and the hole transport layer by applying organic salt, namely formamidinium iodide (FAI), in an eco-friendly isopropanol (IPA) antisolvent to treat the perovskite surface. Incorporating FAI reduces grain boundaries, enhances carrier transportation, and boosts power conversion efficiency from 13.59 % to 15.10 % under 1 sun measurement with an active area of 0.09 cm2. Similarly, under 1000 lx illumination, efficiency improves from 26.70 % to 28.69 %, with enhanced stability. This study offers a cost-effective and low-temperature method via the utilization of carbon electrodes to fabricate highly efficient planar perovskite solar cells under an air atmosphere, showcasing the potential for stable and economically viable photovoltaic solutions.

Accelerating the Development of Thin Film Photovoltaic Technologies: An Artificial Intelligence Assisted Methodology Using Spectroscopic and Optoelectronic Techniques.

Thin film photovoltaic (TFPV) materials and devices present a high complexity with multiscale, multilayer, and multielement structures and with complex fabrication procedures. To deal with this complexity, the evaluation of their physicochemical properties is critical for generating a model that proposes strategies for their development and optimization. However, this process is time-consuming and requires high expertise. In this context, the adoption of combinatorial analysis (CA) and artificial intelligence (AI) strategies represents a powerful asset for accelerating the development of these complex materials and devices. This work introduces a methodology to facilitate the adoption of AI and CA for the development of TFPV technologies. The methodology covers all the necessary steps from the synthesis of samples for CA to data acquisition, AI-assisted data analysis, and the extraction of relevant information for research acceleration. Each step provides details on the necessary concepts, requirements, and procedures and are illustrated with examples from the literature. Then, the application of the methodology to a complex set of samples from a TFPV production line highlights its ability to rapidly glean significant insights even in intricate scenarios. The proposed methodology can be applied to other types of materials and devices beyond PV and using different characterization techniques.

Strain regulates the photovoltaic performance of thick-film perovskites

Perovskite photovoltaics, typically based on a solution-processed perovskite layer with a film thickness of a few hundred nanometres, have emerged as a leading thin-film photovoltaic technology. Nevertheless, many critical issues pose challenges to its commercialization progress, including industrial compatibility, stability, scalability and reliability. A thicker perovskite film on a scale of micrometres could mitigate these issues. However, the efficiencies of thick-film perovskite cells lag behind those with nanometre film thickness. With the mechanism remaining elusive, the community has long been under the impression that the limiting factor lies in the short carrier lifetime as a result of defects. Here, by constructing a perovskite system with extraordinarily long carrier lifetime, we rule out the restrictions of carrier lifetime on the device performance. Through this, we unveil the critical role of the ignored lattice strain in thick films. Our results provide insights into the factors limiting the performance of thick-film perovskite devices.

Fabrication of Pre-Structured Substrates and Growth of CIGS Micro-Absorbers.

Second-generation thin-film Cu(In, Ga)Se2 (CIGS) solar cells are a well-established photovoltaic technology with a record power conversion efficiency of 23.6%. However, their reliance on critical raw materials, such as In and Ga, requires new approaches to reduce the amount of critical raw materials employed. The micro-concentrator concept involves the combination of thin-film photovoltaic technology with concentrator photovoltaic technology. This approach reduces the size of the solar cell to the micrometer range and uses optical concentration to collect sunlight from a larger area, focusing it onto micro solar cells. This work is devoted to the development of a process for manufacturing pre-structured substrates with regular arrays of holes with 200 and 250 µm diameters inside a SiOx insulating matrix. Subsequently, a Cu-In-Ga precursor is deposited by sputtering, followed by photoresist lift-off and the application of a Cu-In-Ga thermal annealing at 500 °C to improve precursor quality and assess pre-structured substrate stability under elevated temperatures. Finally, a two-stage selenization process leads to the formation of CIGS absorber micro-dots. This study presents in detail the fabrication process and explores the feasibility of a bottom-up approach using pre-structured substrates, addressing challenges encountered during fabrication and providing insights for future improvements in CIGS absorber materials.

A simulation and modeling approach of coupled thermal and electrical behavior of PV panels using the artificial hummingbird algorithm and two-dimensional finite difference-based model

Accurate estimation of photovoltaic (PV) panels’ temperature is crucial for an accurate assessment for both the electrical and thermal aspects and performances. In this study we propose an advanced simulation approach linking a double-diode (DD) electrical model using the Artificial hummingbird algorithm; for parameter extraction; and a two-dimensional finite-difference-based thermal model. The electrical-sub model is firstly validated in comparison to experimental data figuring in literature using three types of PV technologies, with a relative error of about 2%. Then, the coupled model is validated using in-situ experimental setup consisting of the usage of thin-film PV technology, temperature sensors, weather station and an infrared camera. The results from both simulations and experiments exhibit strong alignment with a relative error of not higher than 2%; mainly due to the used material calibration uncertainties and external perturbations. This holistic model can be indeed further optimized, still, it has a potential to advance the development in the research area of PV systems.Future efforts could involve additional experimentation to validate the model for different seasons of the year.

Testing the effect of semi-transparent spectrally selective thin film photovoltaics for agrivoltaic application: A multi-experimental and multi-specific approach

The integration of photovoltaic technologies within the agricultural framework, known as agrivoltaics, emerges as a promising and sustainable solution to meet the growing global demands for energy and food production. This innovative technology enables the simultaneous utilization of sunlight for both photovoltaics (PV) and photosynthesis. A key challenge in agrivoltaic research involves identifying technologies applicable to a wide range of plant species and diverse geographic regions. To address this challenge, we adopt a multi-experimental and multi-species approach to assess the viability of semi-transparent, spectrally selective thin-film silicon PV technology. Our findings demonstrate compatibility with crop production in controlled environments for both plants and algae. Notably, selective thin-film PV exhibits the potential to enhance crop yields and serves as a photo-protectant. We observe that plant and algal growth increases beneath the selective PV film when supplemented with appropriate diffuse light in the growth environment. Conversely, in situations where light intensity exceeds optimal levels for plant growth, the selective PV film provides a photo-protective effect. These results suggest potential supplementary benefits of employing this technology in regions characterized by excessive light irradiation, where it can contribute to healthy plant growth.

Breaking the bottleneck of lead-free perovskite solar cells through dimensionality modulation.

The emerging perovskite solar cell (PSC) technology has attracted significant attention due to its superior power conversion efficiency (PCE) among the thin-film photovoltaic technologies. However, the toxicity of lead and poor stability of lead halide materials hinder their commercialization. In this case, after a decade of effort, various categories of lead-free perovskites and perovskite-like materials have been developed, including tin halide perovskites, double perovskites, defect-structured perovskites, and rudorffites. However, the performance of the corresponding devices still falls short of expectations, especially their PCE. The limitations mainly originate from either the unstable lattice structure of these materials, which causes the distortion of their octahedra, or their low dimensionality (e.g., structural and electronic dimensionality)-correlated poor carrier transport and self-trapping effect, accelerating nonradiative recombination. Therefore, understanding the relationship between the structures and performance in these emerging candidates and leveraging these insights to design or modify new lead-free perovskites is of great significance. Herein, we review the variety of dimensionalities in different categories of lead-free perovskites and perovskite-like materials and conclude that dimensionality is an important aspect among the crucial indexes that determine the performance of lead-free PSCs. In addition, we summarize the modulation of both structural and electronic dimensionality, and the corresponding enhanced optoelectronic properties in different categories. Finally, perspectives on the future development of lead-free perovskites and perovskite-like materials for photovoltaic applications are provided. We hope that this review will provide researchers with a concise overview of these emerging materials and help them leverage dimensionality to break the bottleneck in photovoltaic applications.

Crystalline porous materials in perovskite solar cells: a mutually beneficial marriage

Utilization of CPMs across diverse functional layers within Perovskite Solar Cells (PSCs) are systematically classified and analyzed. We scrutinize the correlation between the incorporation of CPMs and the resulting performance of PSC devices.

High-Efficiency Perovskite Solar Cells: Progress and Prospects

The quest for sustainable and efficient energy sources has intensified the exploration of alternative materials and technologies for photovoltaics. As an emerging thin-film photovoltaic technology, chalcogenide solar cells are unanimously at the forefront of research and development due to their excellent light-absorbing capacity, low manufacturing cost, simple structure, and remarkable photovoltaic conversion efficiency. First, this paper reviews the significant progress made in the development of high-efficiency chalcogenide solar cells, including the development of material compositions, device structures, and fabrication techniques that have propelled PSCs to achieve efficiencies over 25%. The paper then highlights innovative approaches in interface engineering, tandem cell configurations, and manufacturing methods that have contributed to the high-efficiency results. While emphasizing efficiency gains, the paper outlines stability challenges, recognizing their role in the practical application of PSC technology. Finally, the paper outlines promising research avenues and technological breakthroughs that could further enhance the efficiency and application of PSCs in the global energy mix, giving them the potential for a wide range of applications in photovoltaic power generation.

Matching the Photocurrent of 2‐Terminal Mechanically‐Stacked Perovskite/Organic Tandem Solar Modules by Varying the Cell Width

Photocurrent matching in conventional monolithic tandem solar cells is achieved by choosing semiconductors with complementary absorption spectra and by carefully adjusting the optical properties of the complete top and bottom stacks. However, for thin film photovoltaic technologies at the module level, another design variable significantly alleviates the task of photocurrent matching, namely the cell width, whose modification can be readily realized by the adjustment of the module layout. Herein, this concept is demonstrated at the experimental level for the first time for a 2T‐mechanically stacked perovskite (FAPbBr3)/organic (PM6:Y6:PCBM) tandem mini‐module, an unprecedented approach for these emergent photovoltaic technologies fabricated in an independent manner. An excellent I sc matching is achieved by tuning the cell widths of the perovskite and organic modules to 7.22 mm (PCE PVKT‐mod = 6.69%) and 3.19 mm (PCE OPV‐mod = 12.46%), respectively, leading to a champion efficiency of 14.94% for the tandem module interconnected in series with an aperture area of 20.25 cm2. Rather than demonstrating high efficiencies at the level of small lab cells, this successful experimental proof‐of‐concept at the module level proves to be particularly useful to couple devices with non‐complementary semiconductors, either in series or in parallel electrical connection, hence overcoming the limitations imposed by the monolithic structure.

High efficiency titanium nitride bowtie nanoparticle and upconverter layer incorporated kesterite tandem solar cell

Thin-film photovoltaic (PV) technology offers an economically viable and flexible way to harness solar energy. Using a material that absorbs more solar light than silicon significantly reduces material consumption and costs. Solar cells based on the kesterite mineral structure and its alloys stand out from other thin-film solar cells due to their earth-abundance and non-toxicity. Incorporating plasmonic nanoparticles in the kesterite absorber layer opens a promising path of enhancing light trapping efficiency. Again, the main losses in solar cells result from the incomplete utilization of the solar spectrum. The otherwise unused sub-bandgap photons can be utilized by adding an upconverting layer on a solar cell. This paper demonstrates a theoretical design and performance analysis of a high-efficiency kesterite solar cell by incorporating titanium nitride (TiN) plasmonic bowtie nanoparticles (NPs) and an upconverter layer. We compared the optical characteristics of various shapes and sizes of nanoparticles to find the optimum solar cell efficiency. The 100 nm thick bowtie-shaped NP had the highest power conversion efficiency, η of 24.80% and had the open circuit voltage Voc=0.59V, and short circuit current density, Jsc = 45.43 mA/cm2. The absorbed power for bowtie-shaped TiN NP incorporation enhanced the average absorption from ∼61% to ∼88% for the kesterite layer. For 100 nm thickness, the absorption enhancement, g, was greater than 1 for the whole spectral range, and the maximum value was ∼1.2. Incorporating a yttrium aluminum garnet upconverter layer increased the solar cell efficiency to ∼27.44.%.

5GSOLAR: The next generation of photovoltaics

5GSOLAR: The next generation of photovoltaics Emerging thin film photovoltaic technologies, currently being developed in research laboratories, are the EU’s key to unlocking its photovoltaic industry and ensuring the growth of a sustainable and green electricity market. The European Green Deal and its Fit for 55 initiative aim to transform Europe into a modern, resource-efficient and competitive economy, ensuring the reduction of net greenhouse gas emissions by at least 55% by 2030, compared to 1990 levels. Solar photovoltaics is considered as one of the cornerstones to achieve a green and carbon-neutral future. As the lowest-cost and most easily deployed clean energy technology, the installed photovoltaic (PV) capacity in Europe has reached almost 195 GW in 2022, and the REPowerEU plan targets to bring online over 320 GW of solar photovoltaic by 2025 and almost 600 GW by 2030.

Heterojunction reconstruction via In doping towards high-efficiency CZTSSe solar cells

The Cu2ZnSn(S,Se)4 solar cells (CZTSSe) are emerging as a hot area of low-cost thin film photovoltaic technology owing to its non-toxicity and excellent photoelectric properties. However, the large open-circuit voltage deficit (Voc,deficit) caused by the inherently defective CdS/ CZTSSe heterojunction interface is still a huge challenge for improving power conversion efficiency. Herein, we reconstruct the heterojunction interface by inserting a CZTSSe:In into the CdS/CZTSSe heterojunction through an In2Se3 post-deposition treatment. The local occupation of In3+ at Zn2+ and Sn4+ sites decreases the disordered Zn- and Sn-related deep defects and generates benign InZn donors within CZITSSe transition layer simultaneously, which effectively enhances the surface p-to-n conversion. The combination of chemical and field-effect passivation regulates the charge extraction and passivates the charge recombination. As a result, the In element-buried absorber enables the Voc boost from 488 to 527 mV with an impressive active-area efficiency of 13.59 %. These results demonstrate the great potential of the In element-buried absorber in alleviating the Voc,deficit and enhancing the performance of CZTSSe solar cells.

Design and simulation of a highly efficient CuBi2O4 thin-film solar cell with hole transport layer

The advancement of thin-film photovoltaic technologies is increasing extensively in today’s world owing to their outstanding optical properties, simple fabrication process, and low-cost. In this work, a solar cell capacitance simulator in one-dimension (SCAPS-1D) has been used to evaluate the output parameters of the heterojunction CuBi2O4-based solar cells with various hole transport layers (HTLs). It is revealed that a p-type cuprous oxide (Cu2O) semiconductor as an HTL ensures proper band alignment at Cu2O/CuBi2O4 interface. The recombination due to minority electrons at the rear side of the CuBi2O4 solar structure with Cu2O HTL can be diminished notably than the device with other HTLs, thus improving the overall outputs of the suggested Cu2O/CuBi2O4/CdS/FTO heterostructure. To realize the behaviors of the proposed PV cell, the thickness and carrier concentration of various films, bulk defects, interface defects, cell resistances, and rear electrode work function of the anticipated CuBi2O4 thin-film photovoltaic device have been optimized. The recombination rates at the interfaces in the proposed heterostructure are also calculated. Moreover, to outline the effects of device input parameters of various materials on vital PV output parameters, adaptable machine learning algorithms have been used to train, test, and calculate the output datasets. High accuracy and low error metrics are confirmed for both the train and test datasets. With 1.0 μm absorber thickness, the efficiency of 29.2% with open-circuit voltage (Voc) of 1.02 V, short-circuit current density (Jsc) of 32.49 mA/cm2, and fill factor (FF) of 87.91% is found for the anticipated solar cell. This investigation suggests that the Cu2O can be effectively employed to scheme a highly efficient, stable, and economical CuBi2O4 solar device.

Towards linking lab and field lifetimes of perovskite solar cells.

Metal halide perovskite solar cells (PSCs) represent a promising low-cost thin-film photovoltaic technology, with unprecedented power conversion efficiencies obtained for both single-junction and tandem applications1-8. To push PSCs towards commercialization, it is critical, albeit challenging, to understand device reliability under real-world outdoor conditions where multiple stress factors (for example, light, heat and humidity) coexist, generating complicated degradation behaviours9-13. To quickly guide PSC development, it is necessary to identify accelerated indoor testing protocols that can correlate specific stressors with observed degradation modes in fielded devices. Here we use a state-of-the-art positive-intrinsic-negative (p-i-n) PSC stack (with power conversion efficiencies of up to approximately 25.5%) to show that indoor accelerated stability tests can predict our six-month outdoor ageing tests. Device degradation rates under illumination and at elevated temperatures are most instructive for understanding outdoor device reliability. We also find that the indium tin oxide/self-assembled monolayer-based hole transport layer/perovskite interface most strongly affects our device operation stability. Improving the ion-blocking properties of the self-assembled monolayer hole transport layer increases averaged device operational stability at 50 °C-85 °C by a factor of about 2.8, reaching over 1,000 h at 85 °C and to near 8,200 h at 50 °C, with a projected 20% degradation, which is among the best to date for high-efficiency p-i-n PSCs14-17.

Copper Nitride: A Versatile Semiconductor with Great Potential for Next-Generation Photovoltaics

Copper nitride (Cu3N) has gained significant attention recently due to its potential in several scientific and technological applications. This study focuses on using Cu3N as a solar absorber in photovoltaic technology. Cu3N thin films were deposited on glass substrates and silicon wafers via radio-frequency magnetron sputtering at different nitrogen flow ratios with total pressures ranging from 1.0 to 5.0 Pa. The thin films’ structural, morphology, and chemical properties were determined using XRD, Raman, AFM, and SEM/EDS techniques. The results revealed that the Cu3N films exhibited a polycrystalline structure, with the preferred orientation varying from 100 to 111 depending on the working pressure employed. Raman spectroscopy confirmed the presence of Cu-N bonds in characteristic peaks observed in the 618–627 cm−1 range, while SEM and AFM images confirmed the presence of uniform and smooth surface morphologies. The optical properties of the films were investigated using UV-VIS-NIR spectroscopy and photothermal deflection spectroscopy (PDS). The obtained band gap, refractive index, and Urbach energy values demonstrated promising optical properties for Cu3N films, indicating their potential as solar absorbers in photovoltaic technology. This study highlights the favourable properties of Cu3N films deposited using the RF sputtering method, paving the way for their implementation in thin-film photovoltaic technologies. These findings contribute to the progress and optimisation of Cu3N-based materials for efficient solar energy conversion.

Thermal and Photo‐Degradation Study of α‐FAPbI3‐Based Perovskite Using In Situ X‐Ray Diffraction

AbstractHybrid halide perovskite has established its credibility as high performance thin film photovoltaic technology. Perovskite based on formamidinium cation is at the core composition to top performances and stability. Herein, a depth study based on temperature‐controlled in situ X‐ray diffraction focusing on the photo‐active formamidinium lead iodide (α‐FAPbI3) is reported. In particular, the thermal stability of the latter and the degradation pathways under different experimental conditions are clarified. Based on this in situ technique, the lattice thermal expansion coefficient is reported that provides relevant information on possible mechanical stress created upon temperature cycling or damp heat test. The results support that α‐FAPbI3 degradation is substantially accelerated when temperature is combined to illumination and when it is interfaced with the extraction layers. In addition, by contrast to in darkness for which α‐FAPbI3 degrades directly into PbI2, the existence of a temperature gap under illumination involving an intermediate step with a non‐crystalline phase resulting from the perovskite degradation and contributing to the formation of PbI2 by‐product is revealed.

Carbon-Based Electrodes for Organic Solar Cells.

Organic solar cells (OSCs) are a promising low-cost thin-film photovoltaic technology while the fabrication of transparent conductive oxide (TCO) and metal electrodes still remains a factor that hinders the scaling-up and commercialization of OSCs. Carbon-based materials are regarded as potential alternatives due to their excellent properties, such as low cost, solution processibility, high conductance, and good chemical stability. In this mini-review, the recent progress of carbon-based materials such as graphite, carbon nanosheets, graphene, and carbon nanotubes to replace the TCO and metal electrodes of OSCs is surveyed. The preparation methods of different carbon-based materials are also discussed. Based on current progress, we summarize the outlooks and challenges of carbon-based electrodes. We anticipate this mini-review will inspire more research efforts to develop high-performance and OSC-matched carbon materials for more efficient and stable carbon-electrode-based OSCs.