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Solar Technologies—A Snapshot of the Editorial Board

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A special issue of Solar (ISSN 2673-9941).

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 42265

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Special Issue Editor

Prof. Dr. Jürgen Heinz Werner

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Guest Editor

Institute for Photovoltaics and Research Center SCoPE, University of Stuttgart, 70569 Stuttgart, Germany
Interests: solar cells; photovoltaics; renewable energy; energy storage; energy conversion; solid-state electronics; semiconductor junctions; opto- and microelectronic materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

It is a pleasure to present the inaugural issue of the editorial board of the new journal Solar. Here, most of the editors contributed an article from their specialist field. The editorial board covers a wide range of expertise and experience in the field of solar sciences and technologies. Consequently, the articles collected here cover not only photovoltaic materials such as silicon, perovskites, and organic semiconductors, but also photovoltaic system technology, and also the thermodynamics of photovoltaic energy conversion. These articles are complemented by a review on the status of photovoltaics in Argentina, as well as by an article on simulation, and, last but not least, an article considering the combination of photovoltaics, heat pumps and energy storage.

We are looking forward to receiving more manuscripts from authors that could make a difference in the spread of solar technologies, including those covering solar thermal technologies and also photovoltaic and solar thermal storage systems.

Prof. Dr. Jürgen Heinz Werner
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Solar is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (13 papers)

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Research

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11 pages, 2802 KiB

Open AccessArticle

Reverse-Bias Defect Creation in Cu(In,Ga)Se₂ Solar Cells and Impact of Encapsulation

by Timon Sebastian Vaas, Bart Elger Pieters, Andreas Gerber and Uwe Rau

Solar 2023, 3(2), 184-194; https://doi.org/10.3390/solar3020012 - 6 Apr 2023

Viewed by 1431

Abstract

Reverse breakdown in Cu(In,Ga)S

e_{2}

Reverse breakdown in Cu(In,Ga)S

e_{2}

(CIGS) solar cells can lead to defect creation and performance degradation. We present pulsed reverse-bias experiments, where we stress CIGS solar cells with a short reverse voltage pulse of ten milliseconds and detect the electrical and thermal response of the cell. This way, we limit the duration of the reverse stress, allowing us to study the initial stages of reverse-bias defect creation in CIGS solar cells and modules. Our results show that permanent damage can develop very fast in under milliseconds. Furthermore, we find the location of defect creation as well as the susceptibility to defect creation under reverse bias depends strongly on whether the cell is encapsulated or not, where encapsulated cells are generally more robust against reverse bias. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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14 pages, 8487 KiB

Open AccessArticle

Interdigitated Back Contact Technology as Final Evolution for Industrial Crystalline Single-Junction Silicon Solar Cell

by Radovan Kopecek, Florian Buchholz, Valentin D. Mihailetchi, Joris Libal, Jan Lossen, Ning Chen, Haifeng Chu, Christoph Peter, Tudor Timofte, Andreas Halm, Yonggang Guo, Xiaoyong Qu, Xiang Wu, Jiaqing Gao and Peng Dong

Solar 2023, 3(1), 1-14; https://doi.org/10.3390/solar3010001 - 22 Dec 2022

Cited by 7 | Viewed by 9608

Abstract

We present our own Interdigitated Back Contact (IBC) technology, which was developed at ISC Konstanz and implemented in mass production with and at SPIC Solar in Xining, China, with production efficiencies of over 24%. To our knowledge, this is the highest efficiency achieved in the mass production of crystalline silicon solar cells without the use of charge-carrier-selective contacts. With an adapted screen-printing sequence, it is possible to achieve open-circuit voltages of over 700 mV. Advanced module technology has been developed for the IBC interconnection, which is ultimately simpler than for conventional double-sided contacted solar cells. In the next step, we will realize low-cost charge-carrier-selective contacts for both polarities in a simple sequence using processes developed and patented at ISC Konstanz. With the industrialisation of this process, it will be possible to achieve efficiencies well above 25% at low cost. We will show that with the replacement of silver screen-printed contacts by copper or aluminium metallisation, future IBC technology will be the end product for the PV market, as it is the best performing c-Si technology, leading to the lowest cost of electricity, even in utility-scale applications. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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13 pages, 2283 KiB

Open AccessArticle

Solar Forecasts Based on the Clear Sky Index or the Clearness Index: Which Is Better?

by Philippe Lauret, Rodrigo Alonso-Suárez, Josselin Le Gal La Salle and Mathieu David

Solar 2022, 2(4), 432-444; https://doi.org/10.3390/solar2040026 - 11 Oct 2022

Cited by 4 | Viewed by 2975

Abstract

In the realm of solar forecasting, it is common to use a clear sky model output to deseasonalise the solar irradiance time series needed to build the forecasting models. However, most of these clear sky models require the setting of atmospheric parameters for which accurate values may not be available for the site under study. This can hamper the accuracy of the prediction models. Normalisation of the irradiance data with a clear sky model leads to the construction of forecasting models with the so-called clear sky index. Another way to normalize the irradiance data is to rely on the extraterrestrial irradiance, which is the irradiance at the top of the atmosphere. Extraterrestrial irradiance is defined by a simple equation that is related to the geometric course of the sun. Normalisation with the extraterrestrial irradiance leads to the building of models with the clearness index. In the solar forecasting domain, most models are built using time series based on the clear sky index. However, there is no empirical evidence thus far that the clear sky index approach outperforms the clearness index approach. Therefore the goal of this preliminary study is to evaluate and compare the two approaches. The numerical experimental setup for evaluating the two approaches is based on three forecasting methods, namely, a simple persistence model, a linear AutoRegressive (AR) model, and a non-linear neural network (NN) model, all of which are applied at six sites with different sky conditions. It is shown that normalization of the solar irradiance with the help of a clear sky model produces better forecasts irrespective of the type of model used. However, it is demonstrated that a nonlinear forecasting technique such as a neural network built with clearness time series can beat simple linear models constructed with the clear sky index. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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13 pages, 2639 KiB

Open AccessArticle

A Comparative Study of Quantum Dot Solar Cell with Two Different ETLs of WS₂ and IGZO Using SCAPS-1D Simulator

by Naureen, Sadanand, Pooja Lohia, Dilip Kumar Dwivedi and Sadia Ameen

Solar 2022, 2(3), 341-353; https://doi.org/10.3390/solar2030020 - 4 Aug 2022

Cited by 6 | Viewed by 2932

Abstract

Quantum dot solar cells have received significant attention in comparison to standard solar cells because of their hybrid nature, low production costs, and higher power conversion efficiency. Although quantum dot solar cells (QDSCs) have several benefits over ordinary solar cells, their performance lags due to carrier combination within the quasi-neutral region (QNR). The electron transport layer (ETL) and hole transport layer (HTL) are the two layers that have the most effect on QDSC performance. This numerical analysis is carried out by using the Solar Cell Capacitance Simulator-1 dimensional software (SCAPS-1D). In this paper, the optimization of two different device structure investigations is performed. In this proposed device structure, WS₂ and IGZO are used as two ETL, CdS is used as a buffer layer, Sb₂Se₃ is used as an absorber layer, and PbS as HTL. Initially, the optimization of the device has been performed, followed by depth analysis of the doping densities. Resistance analysis is also performed to illustrate the effect of resistance on the device. Further, the impact of temperature on the device parameters is also represented, followed by a contour plot between thickness and bandgap for both devices. The impact of the series and shunt resistance on the performance of the solar cell is investigated. The effect of temperature is studied further, and it is observed that the solar device is temperature-sensitive. Finally, the optimized performance with IGZO ETL with PCE of 20.94% is achieved. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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13 pages, 2608 KiB

Open AccessArticle

An Innovative Technique for Energy Assessment of a Highly Efficient Photovoltaic Module

by Filippo Spertino, Gabriele Malgaroli, Angela Amato, Muhammad Aoun Ejaz Qureshi, Alessandro Ciocia and Hafsa Siddiqi

Solar 2022, 2(2), 321-333; https://doi.org/10.3390/solar2020018 - 16 Jun 2022

Cited by 1 | Viewed by 2283

Abstract

For a photovoltaic (PV) generator, knowledge of the parameters describing its equivalent circuit is fundamental to deeply study and simulate its operation in any weather conditions. In the literature, many papers propose methods to determine these parameters starting from experiments. In the most common circuit, there are five of these parameters, and they generally refer to specific weather conditions. Moreover, the dependence on irradiance and temperature is not investigated for the entire set of parameters. In fact, a few papers present some equations describing the dependence of each parameter on weather conditions, but some of their coefficients are unknown. As a consequence, this information cannot be used to predict the PV energy in any individual weather condition. This work proposes an innovative technique to assess the generated energy by PV modules starting from the knowledge of their equivalent parameters. The model is applied to a highly efficient PV generator with all-back contact, monocrystalline silicon technology, and rated power of 370 W. The effectiveness of the model is investigated by comparing its energy prediction with the value estimated by the most common model in the literature to assess PV energy. Generated energy is predicted by assuming PV power to be constant for a time interval of 1 min. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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12 pages, 4217 KiB

Open AccessArticle

Scalable Screen-Printed TiO₂ Compact Layers for Fully Printable Carbon-Based Perovskite Solar Cells

by Dimitrios Raptis, Carys A. Worsley, Simone M. P. Meroni, Adam Pockett, Matthew Carnie and Trystan Watson

Solar 2022, 2(2), 293-304; https://doi.org/10.3390/solar2020016 - 1 Jun 2022

Cited by 2 | Viewed by 3069

Abstract

Fully printable carbon-based perovskite solar cells (C-PSCs) represent some of the most promising perovskite solar cell (PSC) architectures. Highly scalable, stable, and low in cost—these devices consist of a TiO₂ compact layer (C-TiO₂) and three sequentially screen-printed mesoporous layers of TiO₂, ZrO₂, and carbon, through which perovskite is infiltrated. While there has been remarkable progress in optimizing and scaling up deposition of mesoporous layers and perovskite, few publications have focused on optimizing C-TiO₂. In this work, we investigate the potential for substituting commonly used spray pyrolysis with more easily scaled screen-printing. It was found that when comparing layers of similar thickness, 1 cm² devices fabricated with printed C-TiO₂ exhibited similar power conversion efficiency (PCE) to those fabricated with spray pyrolysis. In contrast, thicker-printed C-TiO₂ led to lower efficiency. The influence of TiCl₄ treatment on the quality of produced compact layers was also examined. This proved beneficial, mostly in the printed films, where a champion PCE of 13.11% was attained using screen-printed, TiCl₄ treated C-TiO₂. This work proves that screen-printing is a viable replacement for spray pyrolysis in C-PSCs fabrication. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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19 pages, 3765 KiB

Open AccessArticle

Solar Cells with Laser Doped Boron Layers from Atmospheric Pressure Chemical Vapor Deposition

by Renate Zapf-Gottwick, Sven Seren, Susana Fernandez-Robledo, Evariste-Pasky Wete, Matteo Schiliro, Mohamed Hassan, Valentin Mihailetchi, Thomas Buck, Radovan Kopecek, Jürgen Köhler and Jürgen Heinz Werner

Solar 2022, 2(2), 274-292; https://doi.org/10.3390/solar2020015 - 17 May 2022

Cited by 3 | Viewed by 2707

Abstract

We present laser-doped interdigitated back contact (IBC) solar cells with efficiencies of 23% on an area of 244 cm² metallized by a screen-printed silver paste. Local laser doping is especially suited for processing IBC cells where a multitude of pn-junctions and base contacts lay side by side. The one-sided deposition of boron-doped precursor layers by atmospheric pressure chemical vapor deposition (APCVD) is a cost-effective method for the production of IBC cells without masking processes. The properties of the laser-doped silicon strongly depend on the precursor’s purity, thickness, and the total amount of boron dopants. Variations of the precursor in terms of thickness and boron content, and of the laser pulse energy density, can help to tailor the doping and sheet resistance. With saturation-current densities of 70 fA/cm² at sheet resistances of 60 Ohm/sq, we reached maximum efficiencies of 23% with a relatively simple, industrial process for bifacial IBC-cells, with 70% bifaciality measured on the module level. The APCVD-layers were deposited with an inline lab-type system and a metal transport belt and, therefore, may have been slightly contaminated, limiting the efficiencies when compared to thermal-diffused boron doping. The use of an industrial APCVD system with a quartz glass transport system would achieve even higher efficiencies. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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19 pages, 3745 KiB

Open AccessArticle

How Much Photovoltaic Efficiency Is Enough?

by Jürgen Heinz Werner

Solar 2022, 2(2), 215-233; https://doi.org/10.3390/solar2020012 - 14 Apr 2022

Cited by 3 | Viewed by 2491

Abstract

At present, the purchasing prices for silicon-based photovoltaic modules with 20% efficiency and more are between 20 and 40 EURct/W_p. These numbers correspond to 40 to 80 EUR/m² and are in the same range as the mounting costs (material prices plus salaries) of such modules. Installers and operators of photovoltaic systems carefully balance the module and mounting costs when deciding among modules of different efficiencies. This contribution emulates the installer’s decision via a simple, analytical module mounting decision (Mo²De) model. A priori, the model, and the resulting conclusions are completely independent of the photovoltaically active material inside the modules. De facto, however, based on the present state (cost, efficiency, reliability, bankability, etc.) of modules fabricated from (single) crystalline Si cells, conclusions on other photovoltaic materials might also be drawn: On the one hand, the model suggests that lower-efficiency modules with efficiencies below 20% will be driven out of the market. Keeping in mind their installation costs, installers will ask for large discounts for lower-efficiency modules. Technologies based on organic semiconductors, CdTe, CIGS, and even multicrystalline Si, might not survive in the utility market, or in industrial and residential applications. Moreover, this 20% mark will soon reach 23%, and finally will stop at around 25% for the very best, large-area (square meter sized) commercial modules based on single crystalline silicon only. On the other hand, it also seems difficult for future higher-efficiency modules based on tandem/triple cells to compete with standard Si-based reference modules. Compared to their expected higher efficiency, the production costs of tandem/triple cell modules and, therefore, also their required markup in sales, might be too high. Depending on the mounting cost, the Mo²De-model predicts acceptable markup values of 1 EURct/W_p (for low mounting costs of around 10 EUR/m²) to 11 EURct/W_p (for high mounting costs of 100 EUR/m²) if the module efficiency increases from 23% to 30%. Therefore, a 23% to 24% module efficiency, which is possible with silicon cells alone, might be enough for many terrestrial photovoltaic applications. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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18 pages, 1230 KiB

Open AccessArticle

Photovoltaic System Health-State Architecture for Data-Driven Failure Detection

by Andreas Livera, George Paphitis, Marios Theristis, Javier Lopez-Lorente, George Makrides and George E. Georghiou

Solar 2022, 2(1), 81-98; https://doi.org/10.3390/solar2010006 - 15 Mar 2022

Cited by 8 | Viewed by 3081

Abstract

The timely detection of photovoltaic (PV) system failures is important for maintaining optimal performance and lifetime reliability. A main challenge remains the lack of a unified health-state architecture for the uninterrupted monitoring and predictive performance of PV systems. To this end, existing failure detection models are strongly dependent on the availability and quality of site-specific historic data. The scope of this work is to address these fundamental challenges by presenting a health-state architecture for advanced PV system monitoring. The proposed architecture comprises of a machine learning model for PV performance modeling and accurate failure diagnosis. The predictive model is optimally trained on low amounts of on-site data using minimal features and coupled to functional routines for data quality verification, whereas the classifier is trained under an enhanced supervised learning regime. The results demonstrated high accuracies for the implemented predictive model, exhibiting normalized root mean square errors lower than 3.40% even when trained with low data shares. The classification results provided evidence that fault conditions can be detected with a sensitivity of 83.91% for synthetic power-loss events (power reduction of 5%) and of 97.99% for field-emulated failures in the test-bench PV system. Finally, this work provides insights on how to construct an accurate PV system with predictive and classification models for the timely detection of faults and uninterrupted monitoring of PV systems, regardless of historic data availability and quality. Such guidelines and insights on the development of accurate health-state architectures for PV plants can have positive implications in operation and maintenance and monitoring strategies, thus improving the system’s performance. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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Graphical abstract

11 pages, 2837 KiB

Open AccessArticle

Enhanced Electrical Properties of Alkali-Doped ZnO Thin Films with Chemical Process

by Jaime G. Cuadra, Samuel Porcar, Diego Fraga, Teodora Stoyanova-Lyubenova and Juan B. Carda

Solar 2021, 1(1), 30-40; https://doi.org/10.3390/solar1010004 - 24 Nov 2021

Cited by 2 | Viewed by 2776

Abstract

Doped ZnO are among the most attractive transparent conductive oxides for solar cells because they are relatively cheap, can be textured for light trapping, and readily produced for large-scale coatings. Here, we focus on the development of alternative Na and K-doped ZnO prepared by an easy low-cost spray pyrolysis method for conducting oxide application. To enhance the electrical properties of zinc oxide, alkali-doped Zn_1−x M_xO (x = 0.03) solid solutions were investigated. The resulting layers crystallize in a single hexagonal phase of wurtzite structure with preferred c-axis orientation along a (002) crystal plane. Dense, well attached to the substrate, homogeneous and highly transparent layers were obtained with great optical transmittance higher than 80%. The optical energy band gap of doped ZnO films increase from 3.27 to 3.29 eV by doping with Na and K, respectively. The electrical resistivity of the undoped ZnO could be decreased from 1.03 × 10⁻¹ Ω.cm to 5.64 × 10⁻² Ω.cm (K-doped) and 3.18 × 10⁻² (Na-doped), respectively. Lastly, the carrier concentrations increased from 5.17 × 10¹⁷ (undoped ZnO) to 1 × 10¹⁸ (doped ZnO). Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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Review

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23 pages, 2712 KiB

Open AccessReview

Doing More with Ambient Light: Harvesting Indoor Energy and Data Using Emerging Solar Cells

by Johann Bouclé, Daniel Ribeiro Dos Santos and Anne Julien-Vergonjanne

Solar 2023, 3(1), 161-183; https://doi.org/10.3390/solar3010011 - 20 Mar 2023

Cited by 6 | Viewed by 3832

Abstract

On one side, the capacity of the world’s photovoltaic (PV) systems is experiencing unprecedented growth; on the other side, the number of connected devices is rapidly increasing due to the development of advanced communication technologies. These fields are not completely independent, and recent studies show that indoor energy harvesting is a great candidate for answering the energy challenges of future generations of telecommunications, namely 5G and 6G, ideal for internet-of-things (IoT) scenarios, i.e., smart homes, smart cities, and smart factories. The emerging PV technologies have shown amazing capabilities for indoor energy harvesting, displaying high power conversion efficiency, good flexibility, and champion-specific powers. Recently, the excellent dynamic performance of PV devices enabled them to be used as data receivers in optical wireless communication (OWC) scenarios, calling forth an innovative system able to simultaneously harvest energy and receive communication data with a single PV device. This article reviews the recent literature devoted to the exploitation of photovoltaic technologies for simultaneous indoor energy harvesting and OWC data reception. This contribution highlights the strong potential of the approach toward the next generation of Green IoT systems and the current challenges that need to be addressed with regard to the physics of solar cells, from laboratory to large-scale applications. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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16 pages, 3485 KiB

Open AccessReview

Two-Dimensional Photocatalysts for Energy and Environmental Applications

by Thaleia Ioannidou, Maria Anagnostopoulou and Konstantinos C. Christoforidis

Solar 2022, 2(2), 305-320; https://doi.org/10.3390/solar2020017 - 10 Jun 2022

Cited by 1 | Viewed by 1824

Abstract

The depletion of fossil fuels and onset of global warming dictate the achievement of efficient technologies for clean and renewable energy sources. The conversion of solar energy into chemical energy plays a vital role both in energy production and environmental protection. A photocatalytic approach for H₂ production and CO₂ reduction has been identified as a promising alternative for clean energy production and CO₂ conversion. In this process, the most critical parameter that controls efficiency is the development of a photocatalyst. Two-dimensional nanomaterials have gained considerable attention due to the unique properties that arise from their morphology. In this paper, examples on the development of different 2D structures as photocatalysts in H₂ production and CO₂ reduction are discussed and a perspective on the challenges and required improvements is given. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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Other

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7 pages, 1397 KiB

Open AccessPerspective

Low-Bandgap Mixed Tin–Lead Perovskite Solar Cells

by Jingwei Zhu, Cong Chen and Dewei Zhao

Solar 2022, 2(3), 334-340; https://doi.org/10.3390/solar2030019 - 1 Jul 2022

Cited by 1 | Viewed by 2506

Abstract

Low-bandgap mixed tin (Sn)–lead (Pb) perovskite solar cells have been extensively investigated in the past few years due to their great potential in high-performance perovskite/perovskite tandem solar cells. From this perspective, we briefly summarize the mechanism of understanding of additives and the advances in the efficiency and stability of such low-bandgap Sn-Pb perovskite materials and solar cells in terms of various effective strategies for suppressing the defects and oxidation of Sn²⁺, regulating crystallization growth, etc. We then provide a perspective regarding the achievement of high-quality, low-bandgap Sn-Pb perovskites and highly efficient solar cells. Full article

(This article belongs to the Special Issue Solar Technologies—A Snapshot of the Editorial Board)

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