Eco-Friendly Photovoltaic Materials and Nanocrystal Synthesis

The quest for sustainable solar energy has driven the development of non-toxic, earth-abundant semiconductors that can replace lead-based perovskites and cadmium-containing devices. Central to this effort are colloidal nanocrystals—crystalline particles at the nanometre scale—that offer solution processability, tunable optoelectronic properties and compatibility with low-temperature fabrication. Emerging chalcogenide compositions, notably silver–bismuth sulfide (AgBiS₂) and sodium–bismuth sulfide (NaBiS₂), combine high absorption coefficients and suitable bandgaps with minimal environmental impact. Equally, heavy-pnictogen materials such as copper antimony selenide (CuSbSe₂) exhibit intrinsic stability and delocalised charge transport when engineered at the atomic scale. Advances in synthesis methods—hot-injection growth, cation exchange reactions and surface ligand engineering—have enabled fine control over crystal size, composition and surface chemistry. By tailoring cation distribution, ligand coverage and crystal lattice dynamics, researchers have overcome key challenges of carrier localisation, trap-assisted recombination and ionic migration. These innovations pave the way towards scalable, eco-friendly photovoltaic modules with competitive efficiency and durability, signalling a shift in solar technology towards materials that align performance with environmental stewardship.

Research from Nature Portfolio

Recent studies on NaBiS₂ nanocrystals have revealed that cation disorder not only sharpens optical absorption—with coefficients exceeding 10⁵ cm⁻¹ above a pseudo-direct bandgap of 1.4 eV—but also induces an ultrafast localisation of photogenerated carriers on picosecond timescales, followed by trap-mediated recombination persisting over microseconds. This duality highlights how local disorder can be harnessed to optimise both light harvesting and charge-carrier lifetimes. In parallel, investigations of CuSbSe₂ have uncovered a naturally layered structure that relaxes lattice distortions, combines favourable interlayer bonding and exhibits a low ionic contribution to dielectric screening. These features suppress strong carrier–phonon coupling and enable free-carrier delocalisation, culminating in high mobilities and extended diffusion lengths, thereby charting a design strategy for perovskite-inspired, lead-free absorbers.

Eco-Friendly Photovoltaic Materials and Nanocrystal Synthesis publication trend

The graph below shows the total number of articles in eco-friendly photovoltaic materials and nanocrystal synthesis across all publications each year (not limited to Nature Index journals).

Technical terms

Nanocrystal: A crystalline particle with dimensions in the nanometre range, offering quantum-tunable optical and electronic properties.

Cation disorder: The deliberate randomisation of positively charged ions within a crystal lattice to modify electronic band structure and carrier dynamics.

Ligand exchange: The replacement of molecules bound to a nanocrystal surface to control interparticle coupling, surface passivation and charge transport.

Cation exchange: A synthesis technique wherein one type of cation in a preformed nanocrystal is partially or fully replaced by another to achieve desired composition.

Charge-carrier mobility: A measure of the speed at which electrons or holes move through a semiconductor under an applied electric field.

Absorption coefficient: A parameter quantifying the fraction of light absorbed per unit distance travelled in a material.

References

1. Cation‐Disorder Engineering Promotes Efficient Charge‐Carrier Transport in AgBiS2 Nanocrystal Films. Advanced Materials (2023).
2. Elucidating the Role of Ligand Engineering on Local and Macroscopic Charge‐Carrier Transport in NaBiS2 Nanocrystal Thin Films. Advanced Functional Materials (2024).
3. Strong absorption and ultrafast localisation in NaBiS2 nanocrystals with slow charge-carrier recombination. Nature Communications (2022).
4. Structural and electronic features enabling delocalized charge-carriers in CuSbSe2. Nature Communications (2025).
5. Cation exchange synthesis of AgBiS 2 quantum dots for highly efficient solar cells. Nanoscale (2024).