UCEP Journal and Conference Papers

2025

Journal Papers

  1. Choi, W. J., Ok, Y. W., Upadhyaya, A. D., Min, K. H., Upadhyaya, V. D., Rounsaville, B., … & Rohatgi, A. (2025). Development of 22.5% p-type tunnel oxide passivated contact solar cells through efficiency enhancement by replacing local Al-BSF in PERC cells with (p+) poly-Si/SiO2 carrier selective contact. Solar Energy Materials and Solar Cells, 283, 113436. (https://doi.org/10.1016/j.solmat.2025.113436)
  2. Mouri, T. K., Upadhyaya, A., Rohatgi, A., OK, Y. W., Shafarman, W. N., & Das, U. K. (2025). Microscopic and elemental analysis of temperature-induced changes in sulfur/silicon nitride stack-passivated Si surface. Applied Surface Science, 682, 161557. (https://doi.org/10.1016/j.apsusc.2024.161557)
  3. Hua, A., Upadhyaya, A., Mouri, T. K., Lam, I., Yang, W., Rohatgi, A., … & Heske, C. (2025). Passivation and Degradation of Sulfur-Treated Silicon Surfaces for Photovoltaics. The Journal of Physical Chemistry C. (https://doi.org/10.1021/acs.jpcc.4c07457)

2024

Journal Papers

  1. Min, K. H., Hwang, J. M., Chen, C., Choi, W. J., Upadhyaya, V. D., Bounsaville, B., … & Ok, Y. W. (2024). Enhanced passivation and stability of negative charge injected SiNx with higher nitrogen content on the boron diffused surface of n-type Si solar cells. Solar Energy Materials and Solar Cells, 273, 112922.
  2. Choi, W. J., Ok, Y. W., Madani, K., Upadhyaya, V. D., Upadhyaya, A. D., Rounsaville, B., … & Rohatgi, A. (2024). Development of APCVD BSG and POCl 3 Codiffusion Process for Double-Side TOPCon Solar Cell Precursor Fabrication. IEEE Journal of Photovoltaics, 14, 727
  3. Padhamnath, P., Choi, W. J., De Luna, G., Arcebal, J. D., Rohatgi, A., & Aberle, A. G. (2024). Design and development of front and back contact solar cells with selective poly-Si passivating contact on the front and local Al contact on the rear. Solar Energy Materials and Solar Cells, 269, 112759.
  4. Sinha, A., Dasgupta, S., Rohatgi, A., & Gupta, M. C. (2024). Rapid Thermal Annealing Effects on Passivation Quality of p-TOPCon Silicon Solar Cells. IEEE Journal of Photovoltaics, 14, 226.

Conference Papers

  1. Choi, W. J., Ok, Y. W., Min, K. H., Zhong, R., Dasgupta, S., Upadhyaya, V. D., … & Rohatgi, A. (2024, June). Fabrication and Detailed Analysis of 22.0% Rear Junction Double-side TOPCon Solar Cell with Front SiOx/Polysilicon Selective Emitter. In 2024 IEEE 52nd Photovoltaic Specialist Conference (PVSC)(pp. 1778-1782). IEEE.
  2. Min, K. H., Choi, W. J., Dasgupta, S., Zhong, R., Upadhyaya, V. D., Rounsaville, B., … & Ok, Y. W. (2024, June). Impact of Ex-Situ POCl3 Diffusion on the Passivation Property of n-TOPCon on the Textured Si Wafer. In 2024 IEEE 52nd Photovoltaic Specialist Conference (PVSC)(pp. 1425-1427). IEEE.
  3. Dasgupta, S., Padhamnath, P., Choi, W. J., Ok, Y. W., & Rohatgi, A. (2024, June). Formation of Selective TOPCon Front Surface Field with Excellent Passivation for High-Efficiency Back-Junction Solar Cells. In 2024 IEEE 52nd Photovoltaic Specialist Conference (PVSC)(pp. 1253-1256). IEEE.
  4. Zhong, R., Padhamnath, P., De Luna, G., Arcebal, J. D. D., Upadhyaya, V., Dasgupta, S., … & Rohatgi, A. (2024, June). Characterization and Modeling of Thin N-Type and Thick P-Type Polysilicon Passivated Contacts for Back-Junction Solar Cells. In 2024 IEEE 52nd Photovoltaic Specialist Conference (PVSC)(pp. 843-846). IEEE.
  5. Mitra, S., Johnston, S., Guthrey, H., Hacke, P., Nemeth, B., Dharmadasa, R., … & Stradins, P. (2024, June). Exploring the performance and reliability of screen-printable fire-through copper paste on PERC solar cells. In 2024 IEEE 52nd Photovoltaic Specialist Conference (PVSC)(pp. 1177-1179). IEEE.

2023

Journal Papers

  1. Sinha, A., Dasgupta, S., Rohatgi, A., & Gupta, M. C. (2023). Rapid thermal annealing of p-type polysilicon passivated contacts silicon solar cells. IEEE Journal of Photovoltaics, 13(3), 355-364.
  2. Zhong, R., Padhamnath, P., Choi, W. J., Ok, Y. W., Dasgupta, S., & Rohatgi, A. (2023). Detailed investigation of electrical and optical properties of textured n-type and roughened p-type tunnel oxide passivated contacts for screen-printed double-sided passivated contact silicon solar cell application. Thin Solid Films, 783, 140046.
  3. Padhamnath, P., Choi, W. J., De Luna, G., Arcebal, J. D., & Rohatgi, A. (2023). Design, development and analysis of large-area industrial silicon solar cells featuring a full area polysilicon based passivating contact on the rear and selective passivating contact on the front. Solar Energy Materials and Solar Cells, 256, 112351.
  4. Ok, Y. W., Kim, J. H., Upadhyaya, V. D., Rohatgi, A., Hong, C. H., & Choi, C. J. (2023). Dose-dependency of contact resistance and sheet resistance of B-implanted emitters for N-type crystalline Si solar cells fabricated using screen-printed fire-through Ag/Al paste metallization process. Journal of the Korean Physical Society, 82(7), 707-711.
  5. Tasnim K. Mouri, Ajay Upadhyaya3, Ajeet Rohatgi, Young-Woo Ok, Amandee Hua, Dirk Hauschild, Lothar Weinhardt, Clemens Heske, Vijaykumar Upadhyaya, Brian Rounsaville, William N. Shafarman, Ujjwal K. Das (2023) Hydrogen Sulfide Passivation for p-type Passivated Emitter and Rear Contact (PERC) Solar Cells, accepted by Journal of Photovoltaic. doi: 10.1109/JPHOTOV.2023.3338095.

Conference Papers

  1. Wook-Jin Choi, Young-Woo Ok, Pradeep Padhamnath, Ajay D Upadhyaya1, Gabby De Luna, Kwan Hong Min, Vijaykumar D Upadhyaya, and Ajeet Rohatgi, Investigation and Quantitative Understanding of Front Field Passivation in Rear Junction Selective DS-TOPCon Solar Cells, 2023 IEEE 50th Photovoltaics Specialists Conference (PVSC).
  2. Kwan Hong Min, Jeong-Mo Hwang, Christopher Chen, Wook-Jin Choi, Vijaykumar D Upadhyaya, Brian Rounsaville, Ajeet Rohatgi, and Young-Woo Ok, Investigation of high nitrogen composition SiNx for textured front surface passivation of n-type silicon solar cells in terms of light stability of injected negative charge and cell performance, 2023 IEEE 50th Photovoltaics Specialists Conference (PVSC).
  3. Sagnik Dasgupta, Pradeep Padhamnath, Vijaykumar Upadhyaya, Young-Woo Ok, Kyu-Hyeon Im, and Ajeet Rohatgi, Patterning the Front Polysilicon Contact for Silicon Solar Cells using Laser Oxidation,2023 IEEE 50th Photovoltaics Specialists Conference (PVSC).
  4. Tasnim K. Mouri1, Ajay Upadhyaya, Ajeet Rohatgi, Young-Woo Ok, Amandee Hua, Dirk Hauschild, Lothar Weinhardt, Clemens Heske, William N. Shafarman1, Ujjwal K. Das, ~20% efficient Si PERC solar cell with emitter surface passivated by H2S reaction, 2023 IEEE 50th Photovoltaics Specialists Conference (PVSC).
  5. De Luna, P. Padhamnath, J. D. Arcebal, R. Zhong, A. Rohatgi, A. G. Aberle, Investigation of the Impact of the Wafer Resistivities on Double-Side Passivated Contact Silicon Solar Cells, Abstract submitted to SiliconPV conference 2024.
  6. D. Arcebal, P. Padhamnath, G. De Luna, S. Dasgupta, A. Rohatgi, A.G. Aberle, Investigation of Contact Properties and Device Performance for Bifacial, Double-Side-Textured Silicon Solar Cells with Polysilicon-based Passivating Contacts, Abstract submitted to SiliconPV conference 2024.
  7. Suchismita Mitra, Steve Johnston, Harvey Guthrey, Peter Hacke, Ruvini Dharmadasa, Thad Druffel, Kevin Elmer, Apolo Nambo, Dustin Williams, Ajay Upadhyaya, Vijaykumar D Upadhyaya, Ajeet Rohatgi, Paul Stradins, Evaluating the performance and reliability of screen-printable fire-through copper paste on PERC solar cells, Abstract submitted to SiliconPV conference 2024.

2022

Journal Papers

  1. Chen, C., Hwang, J. M., Ok, Y. W., Choi, W. J., Upadhyaya, V., Rounsaville, B., & Rohatgi, A. (2022). Investigation of long-term light stability of negative charge injected into oxide-nitride-oxide passivation stack of crystalline silicon solar cells. Journal of Applied Physics, 132(21), 213302.
  2. Dasgupta, S., Ok, Y. W., Upadhyaya, V. D., Choi, W. J., Huang, Y. Y., Duttagupta, S., & Rohatgi, A. (2022). Novel Process for Screen-Printed Selective Area Front Polysilicon Contacts for TOPCon Cells Using Laser Oxidation. IEEE Journal of Photovoltaics, 12(6), 1282-1288.
  3. Sinha, A., Dasgupta, S., Rohatgi, A., & Gupta, M. A Rapid Thermal Annealing (RTA) of p-Type Polysilicon Passivated Contacts Silicon Solar Cells, accepted by Journal of Photovoltaic

Conference Papers

  1. Chavez, A., Rummel, B., Jeffries, A., Han, S. M., Bosco, N., Rounsaville, B., & Rohatgi, A. (2022, June). Translating Material-Level Characterization of Carbon-Nanotube-Reinforced Composite Gridlines To Module-Level Degradation. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 0783-0785). IEEE. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC) (pp. 0783-0785). IEEE
  2. Hua, A., Jiang, N., Upadhyaya, A., Lam, I., Mouri, T.K., Hauschild, D., Rohatgi, Ajeet & Heske, C. (2022, June). Chemical surface and interface structure of sulfur-passivated silicon with a SiNx capping layer. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 0076-0076). IEEE.
  3. Sinha, A., Dasgupta, S., Rohatgi, A., & Gupta, M. (2022, June). Rapid Thermal Annealing (RTA) of Hydrogenated Poly-Si under Air and Nitrogen and Blister Formation. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 1168-1168). IEEE.
  4. Mouri, T. K., Upadhyaya, A., Rohatgi, A., Shafarman, W. N., & Das, U. K. (2022, June). Bulk lifetime study of p-type Czochralski silicon with different processing history using quinhydrone-methanol surface passivation. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 1-4). IEEE.
  5. Choi, W. J., Ok, Y. W., Madani, K., Duttagupta, S., & Rohatgi, A. (2022, June). Development of a co-anneal process for double-side TOPCon precursor fabricated by ex-situ POCI3 and APCVD boron diffusion. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 1068-1068). IEEE
  6. Ok, Y. W., Upadhyaya, V. D., Rounsaville, B., Upadhyaya, A. D., Choi, W. J., Rohatgi, A., … & Duttagupta, S. (2022, June). Rear Junction Bifacial Screen-Printed Double Side Passivated Contact Si Solar Cells. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 0251-0253). IEEE.
  7. Dasgupta, S., Ok, Y. W., Upadhyaya, V. D., Choi, W. J., Huang, Y. Y., Duttagupta, S., & Rohatgi, A. (2022, June). Novel Laser Oxidation for Screen-Printed Selective Area Front Poly-Silicon Contacts for TOPCon Cells. In 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)(pp. 0366-0366). IEEE.

2021

Journal Papers

  1. -Y. Huang, Y.-W. Ok, K. Madani, W. Choi, A. Upadhyaya, V. Upadhyaya, B. Rounsaville, V. Chandrasekaran, A. Rohatgi. “~ 23% rear side poly-Si/SiO2 passivated silicon solar cell with optimized ion-implanted boron emitter and screen-printed contacts.” Solar Energy Materials and Solar Cells 230, 111183, 2021.
  2. K. Das, R. Theisen, A. Hua, A. Upadhyaya, I. Lam, T. K. Mouri, N. Jiang, A. Rohatgi. “Efficient passivation of n-type and p-type silicon surface defects by hydrogen sulfide gas reaction.” Journal of Physics: Condensed Matter 33, no. 46, 464002, 2021.
  3. Jain, W. -J. Choi, Y. -Y. Huang, B. Klein and A. Rohatgi, “Design, Optimization, and In-Depth Understanding of Front and Rear Junction Double-Side Passivated Contacts Solar Cells,” in IEEE Journal of Photovoltaics, vol. 11, no. 5, pp. 1141-1148, 2021.
  4. K. Abudayyeh, A. Chavez, S. M. Han, B. Rounsaville, V. Upadhyaya, A. Rohatgi. “Silver-carbon-nanotube composite metallization for increased durability of silicon solar cells against cell cracks.” Solar Energy Materials and Solar Cells, 225, 111017, 2021.
  5. Feng, Eric J. Tervo, D. Vasileska, S. K. Yee, A. Rohatgi, Z. M. Zhang. “Spatial profiles of photon chemical potential in near-field thermophotovoltaic cells.” Journal of Applied Physics 129, no. 21, 213101, 2021.
  6. H. Min, J.‐M. Hwang, E. Cho, H.‐E. Song, S. Park, A. Rohatgi, D. Kim et al. “Analysis of the negative charges injected into a SiO2/SiNx stack using plasma charging technology for field‐effect passivation on a boron‐doped silicon surface.” Progress in Photovoltaics: Research and Applications 29, no. 1, pp54-63, 2021.
  7. Madani, A. Rohatgi, B. Rounsaville, M. -G. Kang, H.-E. Song and Y.-W. Ok, “Enhanced Stability of Exposed PECVD Grown Thin n+ Poly-Si/SiOx Passivating Contacts With Al2O3 Capping Layer During High Temperature Firing,” in IEEE Journal of Photovoltaics, vol. 11, no. 2, pp. 268-272, 2021.

Conference Papers

  1. Ujjwal K. Das, Tasnim K. Mouri, Robert Theisen, Young W. Ok, Ajay Upadhyaya, and Ajeet Rohatgi. “Dopant diffused Si surface passivation by H 2 S gas reaction and quinhydrone-methanol treatment.” In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), 1355-1358. IEEE, 2021.
  2. Ying-Yuan Huang, Aditi Jain, Wook-Jin Choi, Keeya Madani, Young-Woo Ok, and Ajeet Rohatgi. “Modeling and Understanding of Rear Junction Double-Side Passivated Contact Solar Cells with Selective Area TOPCon on Front.” In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), 1971-1976. IEEE, 2021.
  3. Jeong-Mo Hwang, Christopher Chen, Young-Woo Ok, Wookjin Choi, Ajay Upadhyaya, Vijay Upadhyaya, Brian Rounsaville, and Ajeet Rohatgi. “Investigation on Light Stability of Injected Charge in α-SiN x: H by Plasma Charge Injection Technology.” In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), pp. 2119-2123. IEEE, 2021.
  4. Wook-Jin Choi, Keeya Madani, Ying-Yuan Huang, Aditi Jain, Young-Woo Ok, Vijaykumar D. Upadhyaya, Min Gu Kang, Sungjin Choi, and Ajeet Rohatgi. “Optimization of In-situ and Ex-situ doped p+ Passivating Contact for High Efficiency p-TOPCon Solar Cell Application.” In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), pp. 1907-1912. IEEE, 2021.
  5. Andre Chavez, Brian Rummel, Nicolas Dowdy, Sang M. Han, Nick Bosco, Brian Rounsaville, and Ajeet Rohatgi. “Optimization of Carbon-Nanotube-Reinforced Composite Gridlines Towards Commercialization.” In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), pp. 1427-1429. IEEE, 2021.

2020

Journal Papers

  1. Ajeet Rohatgi, Kai Zhu, Jinhui Tong, Dong Hoe Kim, Elsa Reichmanis, Brian Rounsaville, Vivek Prakash, Young-Woo Ok, “26.7% Efficient 4-Terminal Perovskite-Silicon Tandem Solar Cell Composed of a High-Performance Semi-transparent Perovskite Cell and a Doped Poly-Si/SiOx Passivating Contact Silicon Cell”, IEEE Journal of Photovoltaics, vol. 10, no. 2, pp. 417-422, 2020.
  2. Woojun Yoon, David Scheiman, Young-Woo Ok, Zhaoning Song, Glenn Jernigan, Ajeet Rohatgi, Yanfa Yan, and Phillip Jenkins, “Sputtered Indium Tin Oxide as a Recombination Layer Formed on the Tunnel Oxide/Poly-Si Passivating Contact enabling Efficient Monolithic Perovskite/Si Tandem Solar Cells”, Solar Energy Materials and Solar Cells, vol. 210, n110482, 2020,
  3. Ying-Yuan Huang, Keeya Madani, Wookjin Choi, Ajay D Upadhyaya, Vijaykumar D Upadhyaya, Ajeet Rohatgi, Young-Woo Ok, “Fully Screen-Printed Bifacial Large Area 22.6% N-type Si Soar Cell with Lightly Doped Ion-Implanted Boron Emitter and Tunnel Oxide Passivated Rear Contact”, Solar Energy Materials and Solar Cells, vol. 214, n119585, 2020
  4. George C. Wilkes, Ajay D. Upadhyaya, Ajeet Rohatgi, and Mool C. Gupta, “Laser Crystallization and Dopant Activation of a-Si: H Carrier-Selective Layer in TOPCon Si Solar Cells”, IEEE Journal of Photovoltaics 10 (5), p1283-1289, 2020
  5. Keeya Madani, Ajeet Rohatgi, Kwan Hong Min, Hee-eun Song, Ying-Yuan Huang, Ajay D. Upadhyaya, Vijaykumar Upadhyaya, Brian Rounsaville, and Young-Woo Ok. “Comparison of passivation properties of plasma-assisted ALD and APCVD deposited Al2O3 with SiNx capping.” Solar Energy Materials and Solar Cells 218, 110718, 2020

Conference Papers

  1. Aditi Jain, Wook-Jin Choi, Ying-Yuan Huang, Benjamin Klein, and Ajeet Rohatgi, “Design, Optimization, and In-Depth Understanding of Front and Rear Junction Screen-Printed Double-Side Passivated Contacts Soar Cells”, in 2020 47th IEEE Photovoltaic Specialists Conference (PVSC), pp1339-1343, 2020
  2. Ajay D Upadhyaya, Keeya Madani, Vijaykumar Upadhyaya, Brian Rounsaville, and Ajeet Rohatgi, “Boron Selective Emitter formation with un-metallized Joe of 13 fA/cm2 for Silicon Solar Cells Application”, in 2020 47th IEEE Photovoltaic Specialists Conference (PVSC), pp1626-1629, 2020
  3. Wook-Jin Choi, Aditi Jain, Ying-Yuan Huang, Young-Woo Ok, and Ajeet Rohatgi, “Quantitative Understanding and Implementation of Screen-Printed p+ poly-Si/Oxide Passivated Contact to Enhance the Efficiency of p-PERC Cells”, in 2020 47th IEEE Photovoltaic Specialists Conference (PVSC), pp. 0821- 0824, 2020
  4. Ujjwal Das, Robert Theisen, Greg Hanket, Ajay Upadhyaya, Ajeet Rohatgi, Amandee Hua, Lothar Weinhardt, Dirk Hauschild, and Clemens Heske. “Sulfurization as a promising surface passivation approach for both n- and p-type Si.” In 2020 47th IEEE Photovoltaic Specialists Conference (PVSC), pp. 1167-1170, 2020

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