Optical design of structural colored photovoltaics for building integration: From periodic configurations to optimization algorithms Catarina G. Ferreira, Jani Lamminaho, Ananta Paul, Markus Babin, Nanna L. Andersen, Sune Thorsteinsson, Peter B. Poulsen, Karlis Petersons, Leif Yde, Jan F. Stensborg, N. Asger Mortensen, Joel D. Cox, Morten Madsen Nano Energy, 2026 Widespread implementation of building-integrated photovoltaics (BIPVs) requires the design of aesthetically appealing modules that meet the architectural demands of the building, while at the same time complying with electrical and building technical requirements. An effective route to simultaneously address all the needs of BIPVs relies on the use of structural colored elements, capable of realizing different colors without introducing optical absorption losses. In this context, distributed Bragg reflectors (DBRs) have recently attracted enormous attention due to their simple periodic design and color tunability spanning a broad gamut of hues. This work explores the design guidelines of such DBRs but also their main limitations, to finally propose an alternative approach based on optimization algorithms for the inverse design of thin-layer films with non-trivial configurations capable of reproducing any physically realizable color on demand. Using a large scale roll-to-roll (R2R) magnetron sputtering technique, multilayers designed to replicate the color of a clay roof tile were deposited on polymeric foils and applied to silicon photovoltaic mini-modules, exhibiting remarkable color matching and low efficiency losses of less than 18%. This proof-of-concept demonstration paves the way for the use of optimization algorithms and scalable R2R fabrication in the design and development of next-generation colored photovoltaics, possessing fine-tuned customized colors that can be produced with low material consumption.
Structural Colored Planar Multilayers with Minimal Angular Color Dependence for Building Integrated Photovoltaics Catarina G. Ferreira, Ananta Paul, Markus Babin, Jani Lamminaho, Nanna L. Andersen, Sune Thorsteinsson, Peter B. Poulsen, Karlis Petersons, Leif Yde, Jan F. Stensborg, N. Asger Mortensen, Joel D. Cox, Morten Madsen Solar Rrl, 2025 The societal acceptance of building integrated photovoltaics (BIPV) is strongly linked to their visual appearance. In this regard, efforts have been devoted to the design of colored photovoltaic modules that can be esthetically blended into the roofs and façades of buildings. Distributed Bragg reflectors (DBRs), periodically intercalating nonabsorbing dielectric materials with contrasting refractive indices, are one of the most promising technologies currently explored to produce a broad range of vivid structural colors with minimal optical losses. However, DBRs usually exhibit strong color variation with respect to the angles of incident and reflected light, which is undesirable for BIPV applications. To minimize such iridescence, while avoiding the increased design complexity associated with the currently implemented textured substrates, here we developed an alternative approach, relying on an optimization‐based inverse design methodology, to identify nontrivial planar nanometer‐thin layer configurations capable of reproducing different target colors on demand with low angular color dependence. As we demonstrate, these optimized structures consistently outperform the conventional periodic DBRs, meeting the target colors with minimal angular variations in hue, regardless of the color selected, and with very low effect on the photovoltaic performance. Therefore, the proposed approach constitutes a promising route for the design of next‐generation colored BIPV.
Comparative study of industry-compatible indium-oxide-based sputtered transparent electrodes for transparent perovskite solar cells Ananta Paul, Abhijit Singha, Vikas Sharma, Sudhanshu Mallick, Balasubramaniam Kavaipatti, Dinesh Kabra Journal of Physics D Applied Physics, 2025 The growing demand for thin-film optoelectronic and energy-harvesting devices based on sensitive photonic materials, such as organic semiconductors, perovskite, and emerging bioelectronics, has underscored the critical need for low to room temperature (RT) deposition of transparent electrodes (TEs). This study has focused on establishing a deposition mechanism to obtain highly conductive and transparent indium zinc oxide (IZO) and indium tin oxide (ITO) TEs at RT. We have conducted a comparative study between amorphous IZO (a-IZO) and polycrystalline ITO (c-ITO) for applications in transparent perovskite solar cells (T-PSCs). The superstrate-architecture of T-PSCs exhibit better performance with a-IZO as a rear electrode than with c-ITO. The primary reasons behind the improvement in a-IZO-based devices is the low sheet resistance ( 22.41 Ω sq−1), high carrier mobility ( μ = 32.12 cm 2 V − 1 s − 1 ) , low roughness ( RMS ∼ 1.05 nm ), and high transmittance in the infrared range ( T a v ∼ 83.5 % ) compared to c-ITO. This study also presents the first comprehensive understanding of the presence of substantial interface defects which limit the wider adaptation of traditionally used c-ITO in T-PSCs, addressing a significant gap in the literature. Moreover, those interfacial defects have been the primary factor contributing to its lower power conversion efficiency (PCE) of 15.84%, compared to the 18.22% achieved by a-IZO-based devices. Thus, this study elucidates the underlying mechanisms that account for the widespread adoption of a-IZO in the development of T-PSCs.
Optimization of Atomic Layer Deposition Process of Tin Oxide Thin Films for Near-Infrared-Transparent Halide Perovskite Solar Cells Saurabh Gupta, Laxmi Laxmi, Venkatesh G. Chityala, Manas Misra, Ananta Paul, Suryanarayan Nayak, Sudhanshu Mallick, Dinesh Kabra ACS Applied Energy Materials, 2025 Transparent electrodes, typically sputtered transparent conducting oxides (TCOs), are employed in tandem and bifacial perovskite solar cell (PSC) configurations for light transmission. The sputtering process of TCOs’ deposition damages the underlying perovskite and organic charge transporting layers. Tin oxide (SnOx) thin film deposited via atomic layer deposition (ALD) is being used as a buffer layer to prevent damages from high-energy particles and ultraviolet (UV) light during the sputtering process. This study focuses on the optimization of atomic layer deposition (ALD) process parameters for the deposition of SnOx thin films at low temperatures. This work investigates the effects of deposition temperature, precursor exposure, and purge times on the growth behaviors. Structural, optical, and compositional properties of ALD-SnOx thin films are studied in detail as a function of growth parameters. ALD-SnOx (20 nm), deposited via varied recipes, provides films with high average transmittance (>94.8%; 350–1200 nm), varied refractive index (1.78–1.95), negligible extinction coefficient, varied composition of SnOx (x = 1.7–1.95), smooth surfaces (roughness of 0.18–0.28 nm), and high mass density (>5.6 g/cm3), which are suitable to be employed as functional layers in near-infrared (NIR)-transparent PSCs. Further, we apply the optimized SnOx film in NIR-transparent PSCs as a buffer layer for sputtered TCOs.
Optimization of Near Infrared Transparent p-i-n Perovskite Solar Cells with Active Area >1 cm2 for Four-Terminal Perovskite/Si Tandem Solar Cells Laxmi Laxmi, Venkatesh G. Chityala, Suryanarayan Nayak, Ananta Paul, Saurabh Gupta, Manas Misra, Kashimul Hossain, Mohit Kumar Singh, Sudhanshu Mallick, Dinesh Kabra Solar Rrl, 2025 Four‐terminal (4‐T) perovskite/silicon tandem solar cell is crucial due to the different lifetime of top near‐infrared transparent (NIRT) perovskite solar cell (PSC) and bottom silicon (Si) solar cell, and it allows for independent optimization and operation of the top and bottom subcells. Knowing the fact that Si solar cells are well established, we take the opportunity to explore NIRT‐PSC which is still reported by selective groups because of challenges associated with sputtered transparent conducting electrode (TCE) deposition. In this study, we have emphasized on passivation engineering, scalability, modifications to the absorber layer thickness, and advancements in electrode design to improve the performance of NIRT‐PSC. First, we have optimized thickness of passivating aluminum oxide (Al2O3) for p‐i‐n PSCs device with wide bandgap (Eg = 1.67 eV) perovskite absorber. We have achieved power conversion efficiency (PCE) of 20.20% with active area of 0.056 cm2 and 19.16% with active area of 0.175 cm2 by using an optimized thickness of Al2O3 (3 nm) interlayer for opaque devices. Additionally, Al2O3 passivated devices (T80 > 1600 h) demonstrated improved stability compared to control devices (T80 ∼ 100 h) under identical measurement conditions. Building on this optimized passivation strategy, we extended the design to NIRT‐PSCs, which are crucial for 4‐T tandem solar cells. For optimized NIRT‐PSCs, (i) we have used thicker perovskite layer, as TCEs do not provide the benefit of back reflection, and (ii) metallization of transparent conducting electrodes to mitigate higher sheet resistance of TCE compared to opaque electrodes. With optimized NIRT‐PSCs, we have achieved PCE of 29.14% & 26.86% for active areas of 0.175 and 1.08 cm2, respectively, in 4‐T perovskite/Si tandem solar cell, where the bottom Si solar cell has the PCE = 25.5%.
Thermal Stress Mitigation and Improved Performance in Perovskite Solar Cells via Lattice Matched Alkali Halide Passivation Abhijit Singha, Ananta Paul, Nrita Gaur, Harmanjeet Singh Bilkhu, Anuraag Arya, Varun Bhalerao, Sudhanshu Mallick, K. R. Balasubramaniam, Dinesh Kabra Small, 2025 This study utilizes a method to enhance the structural and thermal stability of perovskite solar cells (PSCs) by incorporating an alkali halide interlayer between the electron transport layer (ETL) and perovskite, which is known to improve device efficiency. This passivation technique significantly reduces residual stress within the perovskite at room temperature (3.68 MPa → 2.56 MPa) and maintains structural integrity under thermal cycling (−40 to 85 °C) as per IEC 61215: 2016 standards. Following 50 cycles, the treated film exhibits a minimal increase in residual stress (≈5.34 MPa), in contrast to the control film (≈29.72 MPa) based on Williamson‐Hall 2θ – Sin2Ψ analysis. The incorporation of wide‐bandgap alkali halides facilitates a strong lattice registry, thereby enhancing structural reliability. Moreover, fluorescence lifetime imaging microscopy (FLIM) confirms a reduction in defect formation, correlating with macroscopic lifetime studies. This also increases open circuit voltage (VOC) (1.08 V → 1.15 V) and device efficiency (17.9% → 20.6%). Notably, the treated device retains ≈71% of its initial PCE after 50 thermal cycles, whereas control devices ceased operation after 30 cycles due to thermal stress‐induced interfacial delamination. This approach effectively prevents interlayer delamination, improving long‐term structural reliability and, thereby, enabling efficient and thermally stable PSC deployment.
Inkjet-Printed FASn1-xPbxI3-Based Perovskite Solar Cells Ayush Tara, Vincent Schröder, Ananta Paul, Natalia Maticiuc, Manuel F. Vasquez-Montoya, Janardan Dagar, Susheel Sharma, Rockey Gupta, Emil J. W. List-Kratochvil, Eva L. Unger, Florian Mathies ACS Applied Materials and Interfaces, 2024 Metal halide perovskite solar cells (PSCs) have gained significant attention in thin-film photovoltaic research for their high power conversion efficiency (PCE) and facile fabrication processes. This study presents the use of inkjet printing to fabricate thin films of combinatorial mixed formamidinium tin-lead perovskites and evaluates their layer quality and device performance. Our findings demonstrate that incorporating Pb up to 50% into FASnI3 films enhances lattice stability. The investigation focused on optimizing the composition ratio for improved photovoltaic performance with FASn0.5Pb0.5I3-based PSCs achieving the highest PCE of 10.26%. Additionally, these cells exhibited an absorption spectrum extending beyond 1000 nm, corresponding to a 1.25 eV bandgap. The results suggest that inkjet printing can effectively enhance the efficiency of tin–lead-based PSCs, supporting scalability in device manufacturing.
Quantitative Estimation of Albedo and Tilt Angle Variation in Bifacial Perovskite Solar Cells Ananta Paul, Abhijit Singha, Sakshi Koul, Suryanarayan Nayak, Nrita Gaur, Sudhanshu Mallick, Balasubramaniam Kavaipatti, Dinesh Kabra ACS Applied Materials and Interfaces, 2024 Bifacial perovskite solar cells (Bi-PSCs) have attracted substantial attention within the photovoltaic (PV) community due to their potential for enhanced power generation, suitability for integration into building structures and applicability in multijunction PV systems. This study presents the fabrication of efficient Bi-PSCs and investigates their unique properties using various characterization techniques, including Lambertian reflection effects through tilt angle arrangements and bottom albedo illuminations. The control device achieved a maximum power conversion efficiency (PCE) of 17.46% under front-side 1 Sun AM1.5G illumination. A significant influence of ground Lambertian reflection is observed with tilt angle variations, resulting in an increase in PCE from 17.46% → 18.82% as the tilt angle reached 20°. Additionally, enhancing the rear-side albedo to 0.5 Sun yielded a maximum PCE of 26% with a bifaciality factor of ∼90% at a tilt angle of 20°. Consequently, the synergistic effect of 0.5 Sun albedo and a 20° angular light inclination led to the development of Bi-PSCs with an efficiency of 26.46%. SCAPS-1D simulations are further employed to validate the experimental Lambertian reflection effects. Moreover, the Bi-PSCs exhibited intrinsic self-encapsulation and chemical robustness (T80 for 2000 h in the N2 atmosphere). This study anticipates that cost-effective and highly efficient Bi-PSCs will emerge as a leading PV technology in both single-junction and tandem PV configurations for electricity generation in the near future.
Bandgap-tunable transparent perovskite solar cells for 4T Si/perovskite tandem photovoltaics with PCE> 30% via rational interface management A Singha, T Zhang, A Paul, MM Anas, K Raitani, M Misra, S Manna, ... EES Solar 2 (2), 369-380 , 2026 2026 Citations: 1
Optical design of structural colored photovoltaics for building integration: From periodic configurations to optimization algorithms CG Ferreira, J Lamminaho, A Paul, M Babin, NL Andersen, ... Nano Energy, 111659 , 2025 2025 Citations: 2
Structural Colored Planar Multilayers with Minimal Angular Color Dependence for Building Integrated Photovoltaics CG Ferreira, A Paul, M Babin, J Lamminaho, NL Andersen, ... Solar RRL 9 (23), e202500674 , 2025 2025 Citations: 2
Comparative study of industry-compatible indium-oxide-based sputtered transparent electrodes for transparent perovskite solar cells A Paul, A Singha, V Sharma, S Mallick, B Kavaipatti, D Kabra Journal of Physics D: Applied Physics 58 (41), 415107 , 2025 2025 Citations: 3
Optimization of Atomic Layer Deposition Process of Tin Oxide Thin Films for Near-Infrared-Transparent Halide Perovskite Solar Cells S Gupta, L Laxmi, VG Chityala, M Misra, A Paul, S Nayak, S Mallick, ... ACS Applied Energy Materials 8 (14), 10183-10191 , 2025 2025 Citations: 3
Optimization of Near Infrared Transparent p‐i‐ n Perovskite Solar Cells with Active Area >1 cm 2 for Four‐Terminal Perovskite/Si Tandem Solar Cells L Laxmi, VG Chityala, S Nayak, A Paul, S Gupta, M Misra, K Hossain, ... Solar RRL 9 (12), 2500163 , 2025 2025 Citations: 7
Thermal Stress Mitigation and Improved Performance in Perovskite Solar Cells via Lattice Matched Alkali Halide Passivation A Singha, A Paul, N Gaur, HS Bilkhu, A Arya, V Bhalerao, S Mallick, ... Small 21 (20), 2502659 , 2025 2025 Citations: 8
Predicting Light Scatter in Structural Colored BIPV Modules and Textured Glass Using Radiance NL Andersen, M Babin, J Svatos, K Petersons, L Yde, J Stensborg, ... the 42nd European Photovoltaic Solar Energy Conference and Exhibition in … , 2025 2025
Customizable Colorfoil for Photovoltaic Modules: a New Approach to Aesthetic and Efficient Solar Energy Integration A Paul, J Lamminaho, CG Ferreira, M Babin, K Petersons, NL Andersen, ... the 42nd European Photovoltaic Solar Energy Conference and Exhibition in … , 2025 2025
Protective buffer layer engineering for sputter-resistant transparent perovskite solar cells with improved transmission and efficiency A Singha, A Paul, S Manna, CK Sahoo, V Kumar, A Kottantharayil, ... EES Solar 1 (6), 1160-1172 , 2025 2025 Citations: 1
Numerical Optimization of Structural Colored Interlayers for Building-Integrated Photovoltaics C G Ferreira, J Lamminaho, A Paul, M Babin, N Lysgaard Andersen, ... Proceedings of MATSUS Spring 2025 Conference (MATSUSSpring25) , 2024 2024
Modeling organic electron transport layers in mixed cation tin-based perovskite solar cells A Tara, A Paul, A Singha, S Gohri, J Madan, R Pandey, P Kumar, ... Journal of Nanoparticle Research 26 (12), 278 , 2024 2024 Citations: 4
Inkjet-Printed FASn 1– x Pb x I 3 -Based Perovskite Solar Cells A Tara, V Schröder, A Paul, N Maticiuc, MF Vasquez-Montoya, J Dagar, ... ACS applied materials & interfaces 16 (46), 63520-63527 , 2024 2024 Citations: 9
Quantitative estimation of albedo and tilt angle variation in bifacial perovskite solar cells A Paul, A Singha, S Koul, S Nayak, N Gaur, S Mallick, B Kavaipatti, ... ACS Applied Materials & Interfaces 16 (44), 60258-60267 , 2024 2024 Citations: 14
Could halide perovskites revolutionalise batteries and supercapacitors: A leap in energy storage A Gaurav, A Das, A Paul, A Jain, BD Boruah, M Abdi-Jalebi Journal of Energy Storage 88, 111468 , 2024 2024 Citations: 35
4-T CdTe/perovskite thin film tandem solar cells with efficiency> 24% A Paul, A Singha, K Hossain, S Gupta, M Misra, S Mallick, AH Munshi, ... ACS Energy Letters 9 (6), 3019-3026 , 2024 2024 Citations: 33
Cation exchange enabled improved perovskite infiltration in triple-mesoscopic carbon perovskite solar cells P Kartikay, A Paul, A Yella, S Mallick Materials Chemistry and Physics 307, 128181 , 2023 2023 Citations: 4
NIR-TRANSPARENT ORGANIC AND PEROVSKITE BI-FACIAL OPTOELECTRONIC DEVICES AND PROCESS FOR PREPARATION THEREOF VC Abhijit Singha, Annata Paul, Kavaipatti Ramanathan Balasubramaniam ... 2023
Stable and Efficient Large Area 4T Si/perovskite Tandem Photovoltaics with Sputtered Transparent Contact A Singha, A Paul, S Koul, V Sharma, S Mallick, KR Balasubramaniam, ... Solar RRL , 2023 2023 Citations: 31
Role of Doped Semiconductors in the Catalytic Activity A Gaurav, A Paul, S Dave Trends and Contemporary Technologies for Photocatalytic Degradation of Dyes … , 2022 2022 Citations: 2
MOST CITED SCHOLAR PUBLICATIONS
Correlation of octahedral distortion with vibrational and electronic properties of LaFe1-xTixO3 nanoparticles EG Rini, A Paul, M Nasir, R Amin, MK Gupta, R Mittal, S Sen Journal of Alloys and Compounds 830, 154594 , 2020 2020 Citations: 37
Could halide perovskites revolutionalise batteries and supercapacitors: A leap in energy storage A Gaurav, A Das, A Paul, A Jain, BD Boruah, M Abdi-Jalebi Journal of Energy Storage 88, 111468 , 2024 2024 Citations: 35
4-T CdTe/perovskite thin film tandem solar cells with efficiency> 24% A Paul, A Singha, K Hossain, S Gupta, M Misra, S Mallick, AH Munshi, ... ACS Energy Letters 9 (6), 3019-3026 , 2024 2024 Citations: 33
Stable and Efficient Large Area 4T Si/perovskite Tandem Photovoltaics with Sputtered Transparent Contact A Singha, A Paul, S Koul, V Sharma, S Mallick, KR Balasubramaniam, ... Solar RRL , 2023 2023 Citations: 31
Quantitative estimation of albedo and tilt angle variation in bifacial perovskite solar cells A Paul, A Singha, S Koul, S Nayak, N Gaur, S Mallick, B Kavaipatti, ... ACS Applied Materials & Interfaces 16 (44), 60258-60267 , 2024 2024 Citations: 14
Inkjet-Printed FASn 1– x Pb x I 3 -Based Perovskite Solar Cells A Tara, V Schröder, A Paul, N Maticiuc, MF Vasquez-Montoya, J Dagar, ... ACS applied materials & interfaces 16 (46), 63520-63527 , 2024 2024 Citations: 9
Thermal Stress Mitigation and Improved Performance in Perovskite Solar Cells via Lattice Matched Alkali Halide Passivation A Singha, A Paul, N Gaur, HS Bilkhu, A Arya, V Bhalerao, S Mallick, ... Small 21 (20), 2502659 , 2025 2025 Citations: 8
Optimization of Near Infrared Transparent p‐i‐ n Perovskite Solar Cells with Active Area >1 cm 2 for Four‐Terminal Perovskite/Si Tandem Solar Cells L Laxmi, VG Chityala, S Nayak, A Paul, S Gupta, M Misra, K Hossain, ... Solar RRL 9 (12), 2500163 , 2025 2025 Citations: 7
Modeling organic electron transport layers in mixed cation tin-based perovskite solar cells A Tara, A Paul, A Singha, S Gohri, J Madan, R Pandey, P Kumar, ... Journal of Nanoparticle Research 26 (12), 278 , 2024 2024 Citations: 4
Cation exchange enabled improved perovskite infiltration in triple-mesoscopic carbon perovskite solar cells P Kartikay, A Paul, A Yella, S Mallick Materials Chemistry and Physics 307, 128181 , 2023 2023 Citations: 4
Comparative study of industry-compatible indium-oxide-based sputtered transparent electrodes for transparent perovskite solar cells A Paul, A Singha, V Sharma, S Mallick, B Kavaipatti, D Kabra Journal of Physics D: Applied Physics 58 (41), 415107 , 2025 2025 Citations: 3
Optimization of Atomic Layer Deposition Process of Tin Oxide Thin Films for Near-Infrared-Transparent Halide Perovskite Solar Cells S Gupta, L Laxmi, VG Chityala, M Misra, A Paul, S Nayak, S Mallick, ... ACS Applied Energy Materials 8 (14), 10183-10191 , 2025 2025 Citations: 3
Investigation of structural and dielectric characteristics of La 2 Ni 0.5 Al 0.5 MnO 6 double perovskite ceramics A Paul, M Nasir, PK Mishra, EG Rini, S Sen AIP Conference Proceedings 2220 (1), 040010 , 2020 2020 Citations: 3
Optical design of structural colored photovoltaics for building integration: From periodic configurations to optimization algorithms CG Ferreira, J Lamminaho, A Paul, M Babin, NL Andersen, ... Nano Energy, 111659 , 2025 2025 Citations: 2
Structural Colored Planar Multilayers with Minimal Angular Color Dependence for Building Integrated Photovoltaics CG Ferreira, A Paul, M Babin, J Lamminaho, NL Andersen, ... Solar RRL 9 (23), e202500674 , 2025 2025 Citations: 2
Role of Doped Semiconductors in the Catalytic Activity A Gaurav, A Paul, S Dave Trends and Contemporary Technologies for Photocatalytic Degradation of Dyes … , 2022 2022 Citations: 2
Bandgap-tunable transparent perovskite solar cells for 4T Si/perovskite tandem photovoltaics with PCE> 30% via rational interface management A Singha, T Zhang, A Paul, MM Anas, K Raitani, M Misra, S Manna, ... EES Solar 2 (2), 369-380 , 2026 2026 Citations: 1
Protective buffer layer engineering for sputter-resistant transparent perovskite solar cells with improved transmission and efficiency A Singha, A Paul, S Manna, CK Sahoo, V Kumar, A Kottantharayil, ... EES Solar 1 (6), 1160-1172 , 2025 2025 Citations: 1
Predicting Light Scatter in Structural Colored BIPV Modules and Textured Glass Using Radiance NL Andersen, M Babin, J Svatos, K Petersons, L Yde, J Stensborg, ... the 42nd European Photovoltaic Solar Energy Conference and Exhibition in … , 2025 2025
Customizable Colorfoil for Photovoltaic Modules: a New Approach to Aesthetic and Efficient Solar Energy Integration A Paul, J Lamminaho, CG Ferreira, M Babin, K Petersons, NL Andersen, ... the 42nd European Photovoltaic Solar Energy Conference and Exhibition in … , 2025 2025
