Improved Hole Interfacial Layer for Planar Perovskite Solar Cells with Efficiency Exceeding 15

Planar structure has been proven to be efficient and convenient in fabricating low-temperature and solution-processing perovkite solar cells (PSCs). Interface control and crystal film growth of organometal halide films are regarded as the most important factors to obtain high-performance PSCs. Herein, we report a solution-processed PEDOT:PSS-GeO2 composite films by simply incorporating the GeO2 aqueous solution into the PEDOT:PSS aqueous dispersion as a hole transport layer in planar PSCs. Besides the merits of high conductivity, ambient stability and interface modification of PEDOT:PSS-GeO2 composite films, the formed island-like GeO2 particles are assumed to act as growing sites of crystal nucleus of perovskite films during annealing. By the seed-mediation of GeO2 particles, a superior CH3NH3PbI3–xClx crystalline film with large-scale domains and good film uniformity was obtained. The resulting PSC device with PEDOT:PSS-GeO2 composite film as HTL shows a best performance with 15.15% PCE and a fill facto...