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Compositional engineering of organic-inorganic metal halide perovskite allows for improved optoelectrical properties, however, phase segregation occurs during crystal nucleation and limits perovskite solar cell device performance. Herein, we show that by applying tetrabutylammonium bistriflimide as an additive in the perovskite precursor solution, ultra-uniform perovskite crystals are obtained, which effectively increases device performance. As a result, power conversion efficiencies (PCEs) of 24.5% in a cell and 21.2% in a module are achieved, together with high stability under illumination, humidity and elevated thermal conditions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We observed the crystallization dynamics of halide perovskite crystals (CH3NH3PbI3) by in situ heating wide-angle X-ray scattering measurements. As a result, we revealed that crystal growth occurs during the conversion of complexes to perovskite crystals.

Dithienogermole (DTG) is a germanium-bridged bithiophene system that has been applied as a building unit of conjugated materials for organic electronic devices, including organic photovoltaics and organic light emitting diodes. However, DTG has not been used as a component of sensitizers for dye-sensitized solar cells (DSSCs). In this work, we have synthesized three D-π-A-π-A type sensitizers containing DTG and thiadiazolo[3,4-c]pyridine (PTz). We expected that combining DTG and a strong acceptor PTz would give rise to a strong absorption in the visible region. In addition, we introduced bulky 2-ethylhexyl groups on the germanium atom to prevent dye aggregation on TiO2 films. Three DTG-containing dyes with different anchor units were synthesized and their optical/electrochemical properties were investigated. The DTG-containing dyes exhibited broad and strong absorption bands around 600 nm on TiO2. We fabricated DSSCs based on the DTG-containing dyes. The onsets of incident photon to current conversion efficiency (IPCE) spectra reached 900 nm and a maximal power conversion efficiency of 2.76% was achieved.

Three novel metal-free organic dyes (DN458, DN475 and DN484) were designed for use in plastic-substrate dye-sensitized solar cells (PDSCs). The photoelectric conversion region of DN475 was successfully expanded into the near-infrared region. As a result, an energy conversion efficiency of 5.76% was achieved.

Co-sensitized dye-sensitized solar cells using black dye and a pyridine-anchor dye (NI5 or YNI-2) showing site-selective adsorption behaviour at the TiO2 surface have been prepared for the first time to reduce the competitive adsorption between the two dyes.