Thin-Film Solar Cell Technology

Thin-film solar cell technology exploits layers of semiconductor materials only a few micrometres thick, deposited onto substrates such as glass, metal or flexible polymers. Compared with conventional crystalline silicon cells, thin films offer reduced material consumption, lighter weight and compatibility with roll-to-roll manufacturing. Common absorber materials include copper indium gallium diselenide (CIGS), cadmium telluride (CdTe) and emerging perovskites. Advances in deposition techniques—such as sputtering, co-evaporation and solution processing—have enhanced crystallinity, uniformity and throughput. Bandgap engineering through compositional grading and alloying enables optimisation of light absorption across the solar spectrum, while interface and grain-boundary passivation minimise non-radiative recombination. Integration into tandem architectures further boosts theoretical conversion efficiencies beyond single-junction limits. Globally, thin-film technologies are gaining traction in building-integrated and flexible photovoltaics, contributing to cost-competitive, low-carbon electricity generation and off-grid solutions.

Research from Nature Portfolio

Recent studies have demonstrated that careful elemental engineering of CIGS absorbers can push efficiencies towards 25 per cent. One approach incorporated a significant silver fraction into the CIGS lattice, combined with a steep gallium gradient near the back contact. This design minimises bandgap fluctuations and voltage losses, while a post-deposition rubidium fluoride treatment passivates the absorber surface. The resulting devices achieved certified efficiencies above 23.6 per cent, marking a new record for chalcopyrite-based cells and pointing to further gains through optimised alkali treatments and contact design.

Another investigation provided direct evidence for grain-boundary passivation in CIGS films treated with a sequence of alkali-fluoride post-deposition processes. Nanoscale imaging of surface potential revealed that heavier alkali elements yield stronger passivation, reducing charged defect densities at grain boundaries and correlating with increased open-circuit voltages. Numerical simulations supported the link between local potential changes and device performance, underscoring the critical role of grain-boundary chemistry in high-efficiency polycrystalline photovoltaics.

Thin-Film Solar Cell Technology publication trend

The graph below shows the total number of articles in thin-film solar cell technology across all publications each year (not limited to Nature Index journals).

Technical terms

Chalcopyrite: Crystal structure of CIGS materials characterised by tetragonal lattice symmetry and direct bandgap properties.

Absorber layer: Photoactive semiconductor film that converts incident photons into charge carriers.

Post-deposition treatment: Chemical or thermal process applied after film growth to modify surface and bulk properties.

Grain boundary: Interface between individual crystallites in a polycrystalline film where defects and recombination can concentrate.

Bandgap grading: Spatial variation of semiconductor composition to create a gradient in bandgap energy for enhanced carrier separation.

Passivation: Reduction of electronic defects at surfaces or interfaces to suppress non-radiative recombination.

Tandem solar cell: Stacked configuration combining two or more subcells with different bandgaps to capture a broader range of the solar spectrum.

References

1. High-concentration silver alloying and steep back-contact gallium grading enabling copper indium gallium selenide solar cell with 23.6% efficiency. Nature Energy (2024).
2. Direct evidence for grain boundary passivation in Cu(In,Ga)Se2 solar cells through alkali-fluoride post-deposition treatments. Nature Communications (2019).
3. A review on barrier layers used in flexible stainless-steel based CIGS photovoltaic devices. npj Flexible Electronics (2023).
4. 3D and Multimodal X‐Ray Microscopy Reveals the Impact of Voids in CIGS Solar Cells. Advanced Science (2023).
5. Quasi-Flat Narrow Bandgap Copper Indium Gallium Selenium Bottom Cell Application in Perovskite/Copper Indium Gallium Selenium Tandem Solar Cells. Energy Material Advances (2024).