Abstract: The present disclosure may provide semiconductor perovskite layers and method of making thereof. In some cases, the perovskite layer may comprise a composition of MAn1FAn2Csn3PbX3. MA may be methylammonium, FA may be formamidinium, n1, n2, and n3 may independently be greater than 0 and less than 1, and n1+n2+n3 may equal 1.

Abstract: Wire array solar cells including tandem cells are disclosed. Each solar cell structure in the wire array can comprise a plurality of tandem cells, each tandem cell having multiple junctions separated by tunnel diodes. The junctions in the tandem cell have different bandgaps and are constructed to absorb different light spectra. Typically, each solar cell comprises an inner cell and an outer cell. The bandgap of the inner cell junction is constructed to be lower than the bandgap of the outer cell junction. The absorption and respective thicknesses of the inner and outer cell junctions is chosen so that the series current through the structure is matched in each cell and maximized.