Fabrication of high quality perovskite films by modulating the Pb-O bonds in Lewis acid-base adducts

High efficiency perovskite solar cells can be made through the Lewis adduct approach. The interaction between PbI2 and the Lewis base is a key factor to make high quality perovskite films. Here, we combine a two-step method with the Lewis adduct approach to fabricate high quality organometallic perovskite films by tuning the strength of the Pb-O bond in Lewis acid-base adducts via adding different Lewis base additives. By optimizing the strength of the Pb-O bond, smooth CH3NH3PbI3 films with large perovskite grains are prepared. The high quality CH3NH3PbI3 films lead to a low recombination rate, long carrier life time and highly efficient charge transfer process. As a result, the power conversion efficiency of the best perovskite solar cell increases from 12.79% to 17.26%.