Perovskite materials have emerged as promising candidates for next-generation solar cells, light-emitting diodes, and photodetectors because of their remarkable optical and electronic properties. However, the widespread use of lead-containing perovskites has raised environmental and sustainability concerns. Lead-free halide double perovskites offer an attractive alternative, but their performance is strongly influenced by complex structural, electronic, and defect-related factors.

In this review, Soo-Yeon Yang and Hyojung Kim examine recent advances in 2D and quasi-2D LFHDPs, focusing on how structural design translates into material properties and ultimately device performance. The review goes beyond a conventional classification of perovskite compositions by establishing a structure-property-device performance framework.

Particular attention is given to layered architectures, including Ruddlesden–Popper, Dion–Jacobson, alternating-cation with (111)-oriented structures. The authors discuss how organic spacer cations, crystal orientation, dimensionality, composition, and interfaces influence bandgap, exciton behavior, charge transport, defects, and stability. Quantitative comparisons of optical and electronic properties and representative device performances are also provided to facilitate direct comparison among different LFHDP systems.

The review further highlights the growing potential of layered LFHDPs in photovoltaic, light-emitting, and photodetection applications. For LEDs, special emphasis is placed on exciton-related emission, self-trapped-exciton and dopant-mediated luminescence, photoluminescence quantum yield, and device architecture. Strategies including spacer engineering, compositional tuning, defect passivation, and interface engineering are discussed as routes toward improved device performance.

Despite rapid progress, several challenges remain, including wide or indirect bandgaps, strong exciton binding, limited carrier mobility, defect formation, operational stability, and scalable manufacturing. The review therefore identifies emerging opportunities in AI-assisted materials discovery, high-throughput computational screening, machine learning, green synthesis, multidimensional heterostructures, and industrial-scale processing.

By linking structure → properties → device performance → future engineering strategies, this review provides a practical roadmap for the development of sustainable, high-performance lead-free perovskite optoelectronics. The work entitled “Structure-property relationships in 2D/quasi-2D lead-free halide double perovskites for optoelectronic devices” was published in Frontiers of Optoelectronics (published on Sept. 1, 2026) .