Stolterfoht, M.; Wolff, C.M.; Márquez, J.A.; Zhang, S.; Hages, C.J.; Rothhardt, D.; Albrecht, S.; Burn, P.L.; Meredith, P.; Unold, T.; Neher, D.: Visualization and suppression of interfacial recombination for high-efficiency large-area pin perovskite solar cells. Nature Energy 3 (2018), p. 847–854
10.1038/s41560-018-0219-8

Abstract:
The performance of perovskite solar cells is predominantly limited by non-radiative recombination, either through trap-assisted recombination in the absorber layer or via minority carrier recombination at the perovskite/transport layer interfaces. Here, we use transient and absolute photoluminescence imaging to visualize all non-radiative recombination pathways in planar pin-type perovskite solar cells with undoped organic charge transport layers. We find significant quasi-Fermi-level splitting losses (135 meV) in the perovskite bulk, whereas interfacial recombination results in an additional free energy loss of 80 meV at each individual interface, which limits the open-circuit voltage (VOC) of the complete cell to ~1.12 V. Inserting ultrathin interlayers between the perovskite and transport layers leads to a substantial reduction of these interfacial losses at both the p and n contacts. Using this knowledge and approach, we demonstrate reproducible dopant-free 1 cm2 perovskite solar cells surpassing 20% efficiency (19.83% certified) with stabilized power output, a high VOC (1.17 V) and record fill factor (>81%).