Transparent Electrode and ETL Optimization for Perovskite-based Tandem Solar Cells

Erica Magliano^a, Gemma Giliberti^b, Aldo Di Carlo^a^,^b

^aCNR-ISM Istituto di Struttura Della Materia, Consiglio Nazionale Delle Ricerche, Roma Tor Vergata, Rome, 00133 Italy

^bCHOSE (Centre for Hybrid and Organic Solar Energy) Department of Electronic Engineering, Tor Vergata University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy

Proceedings of MATSUS Fall 2025 Conference (MATSUSFall25)

A6 Advanced materials and device architectures for Transparent PV - #TransparentPV

València, Spain, 2025 October 20th - 24th

Organizers: Aldo Di Carlo and Alejandro Perez-Rodriguez

Poster, Erica Magliano, 344
Publication date: 21st July 2025

Tandem solar cells offer a promising route to surpass the Shockley–Queisser limit of single-junction devices.¹ In conventional n–i–p configurations, spiro-OMeTAD remains the most efficient hole transport layer (HTL), but its high parasitic absorption significantly limits transparency.² The p-i-n configuration of perovskite cells is gaining prominence compared to the n-i-p counterpart in monolithic tandem structures, owing to the extensive progress made from the reduction of recombination losses at perovskite/C60 interface to the superior charge extraction and highly transparency in the HTL side.³

While evaporated C₆₀ typically requires an ALD-deposited SnO₂ layer to protect the stack from sputtering damage, our group has previously introduced a fully solution-processed PCBM/AZO stack, offering a scalable, low-cost alternative.⁴ However, this architecture introduces increased parasitic absorption, particularly from the PCBM and ITO contact, which can compromise overall device performance.

In this work, we optimize the optical and electrical properties of the PCBM/ITO stack through a combination of optical simulations and experimental tuning. For ITO, we evaluate the trade-off between transmittance, thickness, and sheet resistance, investigating the influence on JSC and FF.

For PCBM, we optimize concentration and deposition parameters to improve charge extraction without sacrificing transparency. The effect on VOC and JSC is evaluated. The impact of these optimizations is assessed in tandem devices, with a focus on maximizing photocurrent generation while minimizing optical losses.

These results are highly relevant not only for monolithic tandem architectures but also for the development of transparent perovskite photovoltaics, where maintaining high optical transmittance without compromising electrical performance is crucial, for example, in applications such as building-integrated photovoltaics (BIPV), semi-transparent modules, and integrated electronics. The demonstrated trade-offs and processing strategies represent a significant step toward scalable, industrially relevant perovskite-based PV technologies.

References:

[1] Shockley, W. & Queisser, H. J. Detailed balance limit of efficiency of p-n junction solar cells. J. Appl. Phys. 32, 510–519 (1961).

[2] Nakka, L., Cheng, Y., Aberle, A. G. & Lin, F. Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells. Adv. Energy Sustain. Res. 3, (2022).

[3] Mariotti, S. et al. Interface engineering for high-performance, triple-halide perovskite–silicon tandem solar cells. Science (80-. ). 381, 63–69 (2023).

[4] Mariotti, S. et al. Interface engineering for high-performance, triple-halide perovskite–silicon tandem solar cells. Science (80-. ). 381, 63–69 (2023). 4. Magliano, E. et al. Solution-Processed Metal-Oxide Nanoparticles to Prevent The Sputtering Damage in Perovskite/Silicon Tandem Solar Cells. ACS Appl. Mater. Interfaces 17, 17599–17610 (2025).

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