Molecular Photovoltaics and Perovskite Solar Cells

The talk will address recent developments in molecular photovoltaics and metal-halide perovskite solar cells (PSCs). The recent introduction of of Cu (I/II) complexes both as redox shuttles in liquid electrolytes and solid hole conductors has propelled the open circuit voltage of molecularly sensitized photosystems to over 1 V increasing dramatically their power conversion efficiency (PCE) compared to conventional embodiments. In diffuse day light their PCE exceeds now he performance of GaAs cells opening up new commercial applications. In the rapidly rising PSC area we focus on the mixed electronic-ionic conductivity of pervoskite materials, which causes hysteresis in the current-voltage curve. We discuss latest results on carrier recombination dynamics obtained by electroluminescence measurements. We report on high external quantum yields (ca 3%) and open-circuit voltages larger than 1.2 V, which are exceptional for a material with a bandgap of 1.6 eV and yield to efficiencies >21%. We identify the efficiency limiting processes and propose measures to overcome these.

Speaker: Michael Gratzel, Ecole Ploytechnique Federale de Lausanne