The energy costs associated with separating tightly bound excitons (photoinduced electron-hole pairs) and extracting free charges from highly disordered low-mobility networks represent fundamental losses for many low-cost photovoltaic technologies. We report a low-cost, solution-processable solar cell, based on a highly crystalline perovskite absorber with intense visible to near-infrared absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight. This "meso-superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages of more than 1.1 volts, despite the relatively narrow absorber band gap of 1.55 electron volts. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite.

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Carbon black was employed as the catalyst for triiodide reduction on fluorine-doped tin oxide glass substrates ͑FTO-glass͒ used as counter electrodes in platinum-free dye-sensitized solar cells. The fill factors were strongly dependent on the thickness of the carbon layer, and the light energy conversion efficiency also increased up to a thickness of 10 m. The charge-transfer resistance ͑R ct ͒ of the carbon counter electrode decreased with the thickness of the carbon layer. The R ct for the thicker carbon layer is less than three times that for the platinized FTO-glass. The highest cell efficiency was 9.1% under 100 mW cm −2 light intensity ͑1 sun AM 1.5 light, J sc = 16.8 mA cm −2 , V oc = 789.8 mV, fill factor = 0.685͒.

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