Cs2AgBiBr6 double perovskite thin films were prepared and incorporated into photovoltaic devices featuring power conversion efficiencies close to 2.5%.

Recently developed organic-inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices.

EDOT-OMeTPA was prepared in a simple condensation reaction. When applied to perovskite solar cells, the new hole transporter shows comparable performance to state-of-the-art Spiro-OMeTAD; however the estimated cost contribution is two orders of magnitude lower.

Adding cesium (Cs) and rubidium (Rb) cations to FA0.83MA0.17Pb(I0.83Br0.17)3 hybrid lead halide perovskites results in a remarkable improvement in solar cell performance, but the origin of the enhancement has not been fully understood yet. In this work, Time-of-Flight (ToF), Time-Resolved Microwave Conductivity (TRMC), and Thermally Stimulated Current (TSC) measurements were performed to elucidate the impact of the inorganic cation additives on the trap landscape and charge transport properties within perovskite solar cells. These complementary techniques allow for the assessment of both local features within the perovskite crystals and macroscopic properties of films and full devices. Strikingly, Cs-incorporation was shown to reduce the trap density and charge recombination rates in the perovskite layer. This is consistent with the significant improvements in the open-circuit voltage and fill factor of Cscontaining devices. By comparison, Rb-addition results in an increased charge carrier mobility, which is accompanied by a minor increase in device efficiency and reduced current-voltage hysteresis. By mixing Cs and Rb in quadruple cation (Cs-Rb-FA-MA) perovskites, the advantages of both inorganic cations can be combined. Our study provides valuable insights into the role of these additives in multiple-cation perovskite solar cells, which are essential for the design of highperformance devices.