The recent dramatic rise in power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) has triggered intense research worldwide. However, high PCE values have often been reached with poor stability at an illuminated area of typically less than 0.1 square centimeter. We used heavily doped inorganic charge extraction layers in planar PSCs to achieve very rapid carrier extraction, even with 10- to 20-nanometer-thick layers, avoiding pinholes and eliminating local structural defects over large areas. The robust inorganic nature of the layers allowed for the fabrication of PSCs with an aperture area >1 square centimeter that have a PCE >15%, as certified by an accredited photovoltaic calibration laboratory. Hysteresis in the current-voltage characteristics was eliminated; the PSCs were stable, with >90% of the initial PCE remaining after 1000 hours of light soaking.

Dye-sensitized solar cells (DSCs) using titanium dioxide (TiO 2 ) electrodes with different haze were investigated. It was found that the incident photon to current efficiency (IPCE) of DSCs increases with increase in the haze of the TiO 2 electrodes, especially in the near infrared wavelength region. Conversion efficiency of 11.1%, measured by a public test center, was achieved using high haze TiO 2 electrodes. This indicates that raising the haze of TiO 2 electrodes is an effective technique for improvement of conversion efficiency.

A universally useful idea for preparing high quality perovskite films is proposed by retarding the crystallization of PbI2, which make possible highly reproducible planar structured perovskite solar cells.

A tetrathiafulvalene derivative (TTF-1) was introduced into perovskite solar cells as a dopant-free hole-transporting material, yielding an efficiency over 11%.

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