Resonant perovskite solar cells with extended band edge

Tuning the composition of perovskites to approach the ideal bandgap raises the single-junction Shockley-Queisser efficiency limit of solar cells. The rapid development of narrow-bandgap formamidinium lead triiodide-based perovskites has brought perovskite single-junction solar cell efficiencies up to 26.1%. However, such compositional engineering route has reached the limit of the Goldschmidt tolerance factor. Here, we experimentally demonstrate a resonant perovskite solar cell that produces giant light absorption at the perovskite band edge with tiny absorption coefficients. We design multiple guide-mode resonances by momentum matching of waveguided modes and free-space light via Brillouin-zone folding, thus achieving an 18-nm band edge extension and 1.5 mA/cm(2) improvement of the current. The external quantum efficiency spectrum reaches a plateau of above 93% across the spectral range of similar to 500 to 800 nm. This resonant nanophotonics strategy translates to a maximum EQE-integrated current of 26.0 mA/cm(2) which is comparable to that of the champion single-crystal perovskite solar cell with a thickness of similar to 20 mu m. Our findings break the ray-optics limit and open a new door to improve the efficiency of single-junction perovskite solar cells further when compositional engineering or other carrier managements are close to their limits.

Automated summary

Tuning the composition of perovskites to approach the ideal bandgap has raised the efficiency limit of solar cells. Narrow-bandgap perovskite solar cells have achieved efficiencies of up to 26.1%. However, there is currently a limit to how much the composition can be further engineered.