PEROVSKITE SOLAR CELLS. INFLUENCE OF THE HALOGEN COMPOSITION IN THE PHOTOVOLTAIC PARAMETERS

BELÉN SUÁREZ; VICTORIA GONZALEZ-PEDRO; TERESA S. RIPOLLÉS; RAFAEL S. SÁNCHEZ

Rio Cuarto

Encuentro; VI Encuentro de Física y Química de Superficies; 2014

Universidad Nacional de Rio Cuarto

Perovskite solar cells (PSSCs) have recently emerged as a new class of solar cells that have shown a huge increase in energy efficiency conversion (15-16%) [1], since the first report in 2009 [2]. PSSCs use organometallic halide perovskites as light absorbers, and they are very promising solar materials because they can be made by simple solution processing methods. Also, they present high electron and hole diffusion lengths. The solar cells are formed by a nanoporous metal oxide which is covered with the absorbing material and on top of the last one a hole-transporting material is deposited. Organometallic halide perovkites have the crystal structure ABX3 (like calcium titanate), where A is an organic cation (eg. methyl ammonium), B is Pb, Cd, Cs, and X is a halogen [3,4]. The band gap can easily be modified by changing the halogen ratio (e.g., CH3NH3PbI3−xClx), leading to films with different colors. Here we show the optical characteristics and the photovoltaic parameters of PSSCs in which the perovskite absorbers are formed by methyl ammonium as organic cation, Pd as inorganic cation, and Cl, Br, or I as mixed halides. When perovskites with different I and Br ratios were used, a change in the color of the devices from brown to yellow was observed, suggesting a change in the band gap. The photovoltaic parameters also showed that the short circuit current (Jsc) decreases as the Br/I ratio is increased. Also, the Cl presence in the perovskite structure altered the Jsc which was increased with respect to those containing only Br and/or I.