Numerical simulation of perovskite/perovskite/silicon triple-junction solar cells

Engineering notes

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Chinese explanation / 中文解读

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Original abstract

The global transition to low-carbon electricity is driving rapid growth in photo­ voltaics, where higher module conversion efficiency directly reduces levelized cost of electricity by lowering area-dependent balance-of-system costs. Multi-junction architectures, such as perovskite/silicon dual- and perovskite/perovskite/silicon triple-junctions cells offer a route beyond single-junction limits, yet present added optical, electrical, and manufacturing complexity. Metal-halide perovskites are promising, high-efficiency, low-temperature-processable absorbers but face stabil­ ity and integration challenges. Moreover, current perovskite-based triple-junction devices lag their theoretical potential with a record in 2025 of 30.02 % compared to the theoretical limit of 48.4 %. Therefore, this thesis develops and validates a comprehensive numerical opto- electronic model of perovskite/perovskite/silicon triple-junction solar cells based on an established perovskite/silicon dual-junction model. A Sentaurus TCAD model is used to identify dominant loss mechanisms that limit efficiency and to quantify which targeted improvements yield the largest, most practical gains. Coupling detailed optical modeling with drift-diffusion device physics, the work performs analyses across layer thicknesses, bandgaps, defect densities, transport and tunneling properties. Based on the device analysis, a set of improvement scenarios is acquired. The result is a quantified development roadmap projecting the efficiency gains achievable under each proposed improvement scenario. This roadmap directs experimental efforts toward the most impactful developments. The goal of this research is to accelerate the development of perovskite/perovskite/silicon triple-junction cells toward their theoretical efficiency limits. The analysis is based on a perovskite/perovskite/silicon triple-junction cell built at Fraunhofer ISE. It initially shows a strong current mismatch. By adjusting perovskite layer thicknesses, the perovskite subcells are current-matched, increas­ ing the limiting photocurrent from 8.7 mA cm−2 to 11.8 mA cm−2 and enabling a meaningful per-subcell electrical loss analysis. Electrically, the dominant losses areinterface recombination and limited carrier transport. Improving the HTL of the middle cell removes selectivity losses, while enhancing the ETL mainly increases the internal open-circuit voltage. Combined improvements to the HTL, ETL and bulk lifetime yield a synergistic effect beyond the sum of individual gains. Top cell interface optimization produces a large combined electrical gain by improving the collection efficiency at the ETL. The practical electrical limit for the Fraunhofer ISE cell with perovskite current matching by thickness adjustment is 37.8 %. The comparable cell from EPFL reaches 40.3 %. Achieving full current match for all subcells requires lowering the middle band gap to (1.45 − 1.50) eV and widening the top band gap to (1.97 − 2.00) eV, which raises the matched short-circuit current to 13.3 mA cm−2 . Front-surface texturing and minimizing parasitic layers further push short-circuit current, yielding a practical efficiency potential of 44.6 % for perovskite thicknesses up to 1 500 nm. The theoretical limit for the perovskite/ perovskite/silicon structure is 48.4 %. Ultimately, by identifying the dominant optical and electrical loss mechanisms and quantifying the efficiency gains of targeted improvements, this work delivers an experimentally actionable roadmap showing how perovskite/perovskite/silicon triple-junction cells can reach their potential.

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