Two simple methods to improve tin halide perovskite film structure are introduced, aimed at increasing the power conversion efficiency of lead free perovskite solar cells. First, a hot antisolvent treatment (HAT) was found to increase the film coverage and prevent electrical shunting in the photovoltaic device. Second, it was discovered that annealing under a low partial pressure of dimethyl sulfoxide vapor increased the average crystallite size. The topographical and electrical qualities of the perovskite films are substantively improved as a result of the combined treatments, facilitating the fabrication of tin-based perovskite solar cell devices with power conversion efficiencies of over 7 %.

Perovskite solar cells (PSCs) and organic solar cells (OSCs) are promising renewable light-harvesting technologies with high performance, but the utilization of hazardous dopants and high boiling additives is harmful to all forms of life and the environment. Herein, new multirole π-conjugated polymers (P1-P3) are developed via a rational design approach through theoretical hindsight, further successfully subjecting them into dopant-free PSCs as hole-transporting materials and additive-free OSCs as photoactive donors, respectively. Especially, P3-based PSCs and OSCs not only show high power conversion efficiencies of 17.28% and 8.26%, but also display an excellent ambient stability up to 30 d (for PSCs only), owing to their inherent superior optoelectronic properties in their pristine form. Overall, the rational approach promises to support the development of environmentally and economically sustainable PSCs and OSCs.

A series of solvent-coordinated tin halide complexes were prepared as impurity-free precursors for tin halide perovskites, and their structures were determined by single-crystal X-ray diffraction analysis. Using these precursors, the tin halide perovskites, MASnI 3 and FASnI 3 , were prepared, and their electronic structures and photophysical properties were examined under inert conditions by means of photoelectron yield spectroscopy as well as absorption and fluorescence spectroscopies. Their valence bands (MASnI 3 : −5.02 eV; FASnI 3 : −5.16 eV) are significantly higher than those of MAPbI 3 or the typical hole-transporting materials 2,2′,7,7′-tetrakis( N , N -di- p -methoxyphenylamino)-9,9′-spirobifluorene and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine). These results suggest that to develop the solar cells using these tin halide perovskites with efficient hole-collection properties, hole-transporting materials should be chosen that have the highest occupied molecular orbital levels higher than −5.0 eV.

Herein, we report use of [Li @C ]TFSI as a dopant for spiro-MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10-fold that of conventional devices using Li TFSI . Such high stability is attributed to the hydrophobic nature of [Li @C ]TFSI repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li @C ]TFSI could oxidize spiro-MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000 h while illuminated under ambient conditions.

Grain size control and boundary passivation of perovskite films are the key to obtaining efficient perovskite solar cells.