Issue

Vol. 18 (2026)

Dopant-Free Ultra-Thin Spiro-OMeTAD Enables Near 30%-Efficient n–i–p Perovskite/Silicon Tandem Solar Cells

https://doi.org/10.1007/s40820-025-01962-3
Xiangying Xue
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Weichuang Yang
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Zhiqin Ying
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Fangfang Cao
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Yuheng Zeng
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Zhenhai Yang
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Xi Yang
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China
Jichun Ye
Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (CAS), Ningbo 315201, People’s Republic of China

Corresponding Author: Jichun Ye

jichun.ye@nimte.ac.cn

Nano-Micro Letters, Vol. 18 (2026), Article Number: 116

Abstract

A major challenge for n–i–p structured perovskite/silicon tandem solar cells (TSCs) is the use of 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD), a commonly used hole transport layer, which induces significant optical losses and consequently reduces device current. Herein, we propose an ultra-thin (10 nm) vacuum thermal evaporation (VTE)-deposited spiro-OMeTAD, coupled with a 2D/3D perovskite heterojunction, to simultaneously enhance the optical and electrical properties of n–i–p perovskite/silicon TSCs. Our results demonstrate that the 10-nm-thick spiro-OMeTAD layer significantly improves optical performance, achieving a 92.2% reduction in parasitic absorption and an 18.4% decrease in reflection losses. Additionally, the incorporation of the 2D/3D perovskite heterojunction facilitates improved molecular arrangement and enhanced surface uniformity of the ultrathin spiro-OMeTAD, leading to higher tolerance to interface defects and more efficient hole extraction. Consequently, n–i–p perovskite/silicon TSCs featuring ultrathin spiro-OMeTAD exhibit remarkable efficiencies of 29.73% (0.135 cm2) and 28.77% (28.25% certified efficiency, 1.012 cm2), along with improved stability.


Highlights:
1 Optical loss reduction: The 10-nm-thick vacuum thermal evaporation (VTE)-based 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) film reduces parasitic absorption by 92.2% and reflection losses by 18.4% compared to conventional spin-coated 200-nm-thick spiro-OMeTAD.
2 Electrical performance improvement: The VTE-deposited spiro-OMeTAD, coupled with a 2D/3D perovskite heterojunction, ensures conformal coverage, optimizes energy-level alignment, and passivates interface defects.
3 Device efficiency and stability enhancement of perovskite/silicon tandems: A remarkable efficiency of 29.73% is achieved, the highest reported value for spiro-OMeTAD-based n–i–p tandems, with a 11 times improvement of stability under operational conditions.

Keywords

Perovskite/silicon tandem solar cells Hole transport layers Optical loss reduction Optical design
Xue, Xiangying, Weichuang Yang, Zhiqin Ying, Fangfang Cao, Yuheng Zeng, Zhenhai Yang, Xi Yang, and Jichun Ye. 2026. “Dopant-Free Ultra-Thin Spiro-OMeTAD Enables Near 30%-Efficient n–i–p Perovskite/Silicon Tandem Solar Cells”. Nano-Micro Letters 18 (January):116. https://doi.org/10.1007/s40820-025-01962-3.
Download Citation
Endnote/Zotero/Mendeley (RIS)
BibTeX
References
  1. Best Research−Cell Efficiency Chart. https://www.nrel.gov/pv/cell-efficiency.html. Accessed 05/2025.
  2. X.Y. Chin, D. Turkay, J.A. Steele, S. Tabean, S. Eswara et al., Interface passivation for 31.25%-efficient perovskite/silicon tandem solar cells. Science 381(6653), 59–63 (2023). https://doi.org/10.1126/science.adg0091
  3. E. Aydin, E. Ugur, B.K. Yildirim, T.G. Allen, P. Dally et al., Enhanced optoelectronic coupling for perovskite/silicon tandem solar cells. Nature 623(7988), 732–738 (2023). https://doi.org/10.1038/s41586-023-06667-4
  4. S. Mariotti, E. Köhnen, F. Scheler, K. Sveinbjörnsson, L. Zimmermann et al., Interface engineering for high-performance, triple-halide perovskite-silicon tandem solar cells. Science 381(6653), 63–69 (2023). https://doi.org/10.1126/science.adf5872
  5. L. Mazzarella, Y.-H. Lin, S. Kirner, A.B. Morales-Vilches, L. Korte et al., Infrared light management using a nanocrystalline silicon oxide interlayer in monolithic perovskite/silicon heterojunction tandem solar cells with efficiency above 25%. Adv. Energy Mater. 9(14), 1803241 (2019). https://doi.org/10.1002/aenm.201803241
  6. Z. Ying, Z. Yang, J. Zheng, H. Wei, L. Chen et al., Monolithic perovskite/black-silicon tandems based on tunnel oxide passivated contacts. Joule 6(11), 2644–2661 (2022). https://doi.org/10.1016/j.joule.2022.09.006
  7. P. Tockhorn, J. Sutter, A. Cruz, P. Wagner, K. Jäger et al., Nano-optical designs for high-efficiency monolithic perovskite-silicon tandem solar cells. Nat. Nanotechnol. 17(11), 1214–1221 (2022). https://doi.org/10.1038/s41565-022-01228-8
  8. J. Zheng, H. Wei, Z. Ying, X. Yang, J. Sheng et al., Balancing charge-carrier transport and recombination for perovskite/TOPCon tandem solar cells with double-textured structures. Adv. Energy Mater. 13(5), 2203006 (2023). https://doi.org/10.1002/aenm.202203006
  9. B. Chen, Z.J. Yu, S. Manzoor, S. Wang, W. Weigand et al., Blade-coated perovskites on textured silicon for 26%-efficient monolithic perovskite/silicon tandem solar cells. Joule 4(4), 850–864 (2020). https://doi.org/10.1016/j.joule.2020.01.008
  10. M. Zhang, Z. Ying, X. Li, S. Li, L. Chen et al., Hole-selective transparent in situ passivation contacts for efficient and stable n–i–p graded perovskite/silicon tandem solar cells. Adv. Mater. 37(14), 2416530 (2025). https://doi.org/10.1002/adma.202416530
  11. T. Leijtens, K.A. Bush, R. Prasanna, M.D. McGehee, Opportunities and challenges for tandem solar cells using metal halide perovskite semiconductors. Nat. Energy 3(10), 828–838 (2018). https://doi.org/10.1038/s41560-018-0190-4
  12. M.H. Futscher, B. Ehrler, Efficiency limit of perovskite/Si tandem solar cells. ACS Energy Lett. 1(4), 863–868 (2016). https://doi.org/10.1021/acsenergylett.6b00405
  13. E. Ugur, A. Ali Said, P. Dally, S. Zhang, C.E. Petoukhoff et al., Enhanced cation interaction in perovskites for efficient tandem solar cells with silicon. Science 385(6708), 533–538 (2024). https://doi.org/10.1126/science.adp1621
  14. H. Yang, Y. Shen, G. Xu, F. Yang, X. Wu et al., Functional spiro-OMeTAD-like dopant for Li-ion-free hole transport layer to develop stable and efficient n-i-p perovskite solar cells. Nano Energy 119, 109033 (2024). https://doi.org/10.1016/j.nanoen.2023.109033
  15. L. Ye, J. Wu, S. Catalán-Gómez, L. Yuan, R. Sun et al., Superoxide radical derived metal-free spiro-OMeTAD for highly stable perovskite solar cells. Nat. Commun. 15(1), 7889 (2024). https://doi.org/10.1038/s41467-024-52199-4
  16. X. Luo, D. Gao, D. Zhang, G. Zhou, Y. Guo et al., Highly soluble and oxidizing organic salts doped hole-transporting layer enables efficient and stable perovskite solar cells. Adv. Funct. Mater. 35(30), 2425038 (2025). https://doi.org/10.1002/adfm.202425038
  17. F. Hou, L. Yan, B. Shi, J. Chen, S. Zhu et al., Monolithic perovskite/silicon-heterojunction tandem solar cells with open-circuit voltage of over 1.8 V. ACS Appl. Energy Mater. 2(1), 243–249 (2019). https://doi.org/10.1021/acsaem.8b00926
  18. X. Sallenave, M. Shasti, E.H. Anaraki, D. Volyniuk, J.V. Grazulevicius et al., Interfacial and bulk properties of hole transporting materials in perovskite solar cells: spiro-MeTAD versus spiro-OMeTAD. J. Mater. Chem. A 8(17), 8527–8539 (2020). https://doi.org/10.1039/D0TA00623H
  19. J. Zheng, W. Duan, Y. Guo, Z.C. Zhao, H. Yi et al., Efficient monolithic perovskite–Si tandem solar cells enabled by an ultra-thin indium tin oxide interlayer. Energy Environ. Sci. 16(3), 1223–1233 (2023). https://doi.org/10.1039/D2EE04007G
  20. L. Wang, H. Zhou, N. Li, Y. Zhang, L. Chen et al., Carrier transport composites with suppressed glass-transition for stable planar perovskite solar cells. J. Mater. Chem. A 8(28), 14106–14113 (2020). https://doi.org/10.1039/D0TA03376F
  21. L. Wang, Q. Song, F. Pei, Y. Chen, J. Dou et al., Strain modulation for light-stable n-i-p perovskite/silicon tandem solar cells. Adv. Mater. 34(26), e2201315 (2022). https://doi.org/10.1002/adma.202201315
  22. M.J. Jeong, J.H. Lee, C.H. You, S.Y. Kim, S. Lee et al., Oxide/halide/oxide architecture for high performance semi-transparent perovskite solar cells. Adv. Energy Mater. 12(31), 2200661 (2022). https://doi.org/10.1002/aenm.202200661
  23. E. Ugur, E. Aydin, M. De Bastiani, G.T. Harrison, B.K. Yildirim et al., Front-contact passivation through 2D/3D perovskite heterojunctions enables efficient bifacial perovskite/silicon tandem solar cells. Matter 6(9), 2919–2934 (2023). https://doi.org/10.1016/j.matt.2023.05.028
  24. E. Aydin, J. Liu, E. Ugur, R. Azmi, G.T. Harrison et al., Ligand-bridged charge extraction and enhanced quantum efficiency enable efficient n–i–p perovskite/silicon tandem solar cells. Energy Environ. Sci. 14(8), 4377–4390 (2021). https://doi.org/10.1039/D1EE01206A
  25. G. Du, L. Yang, P. Dong, L. Qi, Y. Che et al., Sequential molecule-doped hole conductor to achieve >23% perovskite solar cells with 3000-hour operational stability. Adv. Mater. 35(35), 2303692 (2023). https://doi.org/10.1002/adma.202303692
  26. G. Du, L. Yang, J. Zhang, Light soaking induced halide doping of evaporated spiro-OMeTAD in perovskite solar cells. Laser Photon. Rev. 17(1), 2200475 (2023). https://doi.org/10.1002/lpor.202200475
  27. J. Zheng, Z. Ying, Z. Yang, Z. Lin, H. Wei et al., Polycrystalline silicon tunnelling recombination layers for high-efficiency perovskite/tunnel oxide passivating contact tandem solar cells. Nat. Energy 8(11), 1250–1261 (2023). https://doi.org/10.1038/s41560-023-01382-w
  28. W. Yang, Z. Yang, C. Shou, J. Sheng, B. Yan et al., Optical design and optimization for back-contact perovskite solar cells. Sol. Energy 201, 84–91 (2020). https://doi.org/10.1016/j.solener.2020.02.099
  29. G. Yu, C. Shou, Z. Yang, H. He, Y. Zhang et al., Optical management of spacer layer of high-performance four-terminal perovskite/silicon tandem solar cells. Sol. Energy 228, 226–234 (2021). https://doi.org/10.1016/j.solener.2021.09.018
  30. A. Al-Ashouri, E. Köhnen, B. Li, A. Magomedov, H. Hempel et al., Monolithic perovskite/silicon tandem solar cell with >29% efficiency by enhanced hole extraction. Science 370(6522), 1300–1309 (2020). https://doi.org/10.1126/science.abd4016
  31. P. Schulz, J.O. Tiepelt, J.A. Christians, I. Levine, E. Edri et al., High-work-function molybdenum oxide hole extraction contacts in hybrid organic-inorganic perovskite solar cells. ACS Appl. Mater. Interfaces 8(46), 31491–31499 (2016). https://doi.org/10.1021/acsami.6b10898
  32. H. Liu, R. Lang, S. Jiang, W. Lu, W. Zhang et al., Bifacial semitransparent perovskite solar cells with MoOx/Cu/Ag/MoOx multilayer transparent electrode. Sol. Energy 228, 290–298 (2021). https://doi.org/10.1016/j.solener.2021.09.065
  33. F. Hou, Y. Li, L. Yan, B. Shi, N. Ren et al., Control perovskite crystals vertical growth for obtaining high-performance monolithic perovskite/silicon heterojunction tandem solar cells with VOC of 1.93 V. Solar RRL 5(10), 2100357 (2021). https://doi.org/10.1002/solr.202100357
  34. L. Yang, Y. Jin, Z. Fang, J. Zhang, Z. Nan et al., Efficient semi-transparent wide-bandgap perovskite solar cells enabled by pure-chloride 2D-perovskite passivation. Nano-Micro Lett. 15(1), 111 (2023). https://doi.org/10.1007/s40820-023-01090-w
  35. G. Du, L. Yang, C. Zhang, X. Zhang, N. Rolston et al., Evaporated undoped spiro-OMeTAD enables stable perovskite solar cells exceeding 20% efficiency. Adv. Energy Mater. 12(22), 2103966 (2022). https://doi.org/10.1002/aenm.202103966
  36. W. Luo, C. Wu, D. Wang, Z. Zhang, X. Qi et al., Dopant-free Spiro-OMeTAD as hole transporting layer for stable and efficient perovskite solar cells. Org. Electron. 74, 7–12 (2019). https://doi.org/10.1016/j.orgel.2019.06.039
  37. G.-W. Kim, D.V. Shinde, T. Park, Thickness of the hole transport layer in perovskite solar cells: performance versus reproducibility. RSC Adv. 5(120), 99356–99360 (2015). https://doi.org/10.1039/C5RA18648J
  38. N. Marinova, W. Tress, R. Humphry-Baker, M.I. Dar, V. Bojinov et al., Light harvesting and charge recombination in CH3NH3PbI3 perovskite solar cells studied by hole transport layer thickness variation. ACS Nano 9(4), 4200–4209 (2015). https://doi.org/10.1021/acsnano.5b00447
  39. N. Shibayama, H. Maekawa, Y. Nakamura, Y. Haruyama, M. Niibe et al., Control of molecular orientation of spiro-OMeTAD on substrates. ACS Appl. Mater. Interfaces 12(44), 50187–50191 (2020). https://doi.org/10.1021/acsami.0c15509
  40. H. Kanda, N. Shibayama, A.J. Huckaba, Y. Lee, S. Paek et al., Band-bending induced passivation: high performance and stable perovskite solar cells using a perhydropoly(silazane) precursor. Energy Environ. Sci. 13(4), 1222–1230 (2020). https://doi.org/10.1039/C9EE02028D
  41. W. Yang, B. Ding, Z. Lin, J. Sun, Y. Meng et al., Visualizing interfacial energy offset and defects in efficient 2D/3D heterojunction perovskite solar cells and modules. Adv. Mater. 35(35), 2302071 (2023). https://doi.org/10.1002/adma.202302071
  42. S. Jeong, S. Seo, H. Yang, H. Park, S. Shin et al., Cyclohexylammonium-based 2D/3D perovskite heterojunction with funnel-like energy band alignment for efficient solar cells (23.91%). Adv. Energy Mater. 11(42), 2102236 (2021). https://doi.org/10.1002/aenm.202102236
  43. D. Shi, X. Qin, Y. Li, Y. He, C. Zhong et al., Spiro-OMeTAD single crystals: remarkably enhanced charge-carrier transport via mesoscale ordering. Sci. Adv. 2(4), e1501491 (2016). https://doi.org/10.1126/sciadv.1501491
  44. P. Fassl, Y. Zakharko, L.M. Falk, K.P. Goetz, F. Paulus et al., Effect of density of surface defects on photoluminescence properties in MAPbI3 perovskite films. J. Mater. Chem. C 7(18), 5285–5292 (2019). https://doi.org/10.1039/C8TC05998E
  45. H. Tsai, D. Ghosh, W. Panaccione, L.-Y. Su, C.-H. Hou et al., Addressing the voltage induced instability problem of perovskite semiconductor detectors. ACS Energy Lett. 7(11), 3871–3879 (2022). https://doi.org/10.1021/acsenergylett.2c02054
  46. Y. Zhang, C. Zhou, L. Lin, F. Pei, M. Xiao et al., Gelation of hole transport layer to improve the stability of perovskite solar cells. Nano-Micro Lett. 15(1), 175 (2023). https://doi.org/10.1007/s40820-023-01145-y
  47. X. Liu, B. Zheng, L. Shi, S. Zhou, J. Xu et al., Perovskite solar cells based on spiro-OMeTAD stabilized with an alkylthiol additive. Nat. Photonics 17(1), 96–105 (2023). https://doi.org/10.1038/s41566-022-01111-x
  48. S. Zhang, S.M. Hosseini, R. Gunder, A. Petsiuk, P. Caprioglio et al., The role of bulk and interface recombination in high-efficiency low-dimensional perovskite solar cells. Adv. Mater. 31(30), 1901090 (2019). https://doi.org/10.1002/adma.201901090
  49. S.N. Habisreutinger, B. Wenger, H.J. Snaith, R.J. Nicholas, Dopant-free planar n–i–p perovskite solar cells with steady-state efficiencies exceeding 18%. ACS Energy Lett. 2(3), 622–628 (2017). https://doi.org/10.1021/acsenergylett.7b00028
  50. Y. Bao, T. Ma, Z. Ai, Y. Zhang, L. Shi et al., Insights into efficiency deviation from current-mismatch for tandem photovoltaics. Nano Energy 120, 109165 (2024). https://doi.org/10.1016/j.nanoen.2023.109165
  51. T. Kirchartz, J.A. Márquez, M. Stolterfoht, T. Unold, Photoluminescence-based characterization of halide perovskites for photovoltaics. Adv. Energy Mater. 10(26), 1904134 (2020). https://doi.org/10.1002/aenm.201904134
  52. F. Staub, H. Hempel, J.-C. Hebig, J. Mock, U.W. Paetzold et al., Beyond bulk lifetimes: insights into lead halide perovskite films from time-resolved photoluminescence. Phys. Rev. Appl. 6(4), 044017 (2016). https://doi.org/10.1103/physrevapplied.6.044017
  53. B. Krogmeier, F. Staub, D. Grabowski, U. Rau, T. Kirchartz, Quantitative analysis of the transient photoluminescence of CH3NH3PbI3/PC61BM heterojunctions by numerical simulations. Sustain. Energy Fuels 2(5), 1027–1034 (2018). https://doi.org/10.1039/c7se00603a
  54. X. Li, Z. Ying, S. Li, L. Chen, M. Zhang et al., Top-down dual-interface carrier management for highly efficient and stable perovskite/silicon tandem solar cells. Nano-Micro Lett. 17(1), 141 (2025). https://doi.org/10.1007/s40820-024-01631-x
  55. X. Liu, Z. Yu, T. Wang, K.L. Chiu, F. Lin et al., Full defects passivation enables 21% efficiency perovskite solar cells operating in air. Adv. Energy Mater. 10(38), 2001958 (2020). https://doi.org/10.1002/aenm.202001958
  56. M. Wang, Z. Shi, C. Fei, Z.J.D. Deng, G. Yang et al., Ammonium cations with high pKa in perovskite solar cells for improved high-temperature photostability. Nat. Energy 8(11), 1229–1239 (2023). https://doi.org/10.1038/s41560-023-01362-0
  57. M.V. Khenkin, E.A. Katz, A. Abate, G. Bardizza, J.J. Berry et al., Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures. Nat. Energy 5(1), 35–49 (2020). https://doi.org/10.1038/s41560-019-0529-5
  58. X. Shen, X. Lin, Y. Peng, Y. Zhang, F. Long et al., Two-dimensional materials for highly efficient and stable perovskite solar cells. Nano-Micro Lett. 16(1), 201 (2024). https://doi.org/10.1007/s40820-024-01417-1
  59. J. Wen, Y. Zhao, P. Wu, Y. Liu, X. Zheng et al., Heterojunction formed via 3D-to-2D perovskite conversion for photostable wide-bandgap perovskite solar cells. Nat. Commun. 14(1), 7118 (2023). https://doi.org/10.1038/s41467-023-43016-5
  60. W. Yang, H. Long, X. Sha, J. Sun, Y. Zhao et al., Unlocking voltage potentials of mixed-halide perovskite solar cells via phase segregation suppression. Adv. Funct. Mater. 32(12), 2110698 (2022). https://doi.org/10.1002/adfm.202110698
  61. J. Warby, F. Zu, S. Zeiske, E. Gutierrez-Partida, L. Frohloff et al., Understanding performance limiting interfacial recombination in pin perovskite solar cells. Adv. Energy Mater. 12(12), 2103567 (2022). https://doi.org/10.1002/aenm.202103567
Read More
Author biographies are not available.
Download this PDF file
PDF SUPPLEMENTARY FILE

Most read articles by the same author(s)