Monolithic all-perovskite tandem solar cells present a promising approach for exceeding the efficiency limit of single-junction solar cells. However, the substantial open-circuit voltage loss in the wide-bandgap perovskite subcell hinders further improvements in power-conversion efficiency. Now, researchers from China's Nanjing University, Renshine Solar (Suzhou) and Ecole Polytechnique Fédérale de Lausanne (EPFL) have developed wide-bandgap perovskite films with improved crystal orientation that suppress non-radiative recombination.
The team showed that using two-dimensional perovskite as an intermediate phase on the film surface promotes heterogeneous nucleation along the three-dimensional perovskite facets during crystallization. Preferred orientations can be realized by augmenting the quantity of two-dimensional phases through surface composition engineering, without the need for excessive two-dimensional ligands that otherwise impede carrier transport.
The scientists demonstrated an open-circuit voltage of 1.373 V for 1.78 eV wide-bandgap perovskite solar cells, along with a high fill factor of 84.7%.
This yields an open-circuit voltage of 2.21 V and a certified power-conversion efficiency of 29.1% for all-perovskite tandem solar cells, measured under the maximum power-point conditions.
