TiO₂ aerogel as interlock layer improves thermal stability in perovskite solar cells

Despite the high efficiency values reported recently for organometallic perovskite solar cells, there are still drawbacks related to the instability of these devices in humid environments and sudden temperature variations. Specifically, the instability due to temperature variations may be related to the phase transition of CH3NH3PbI3 perovskite (similar to 54 degrees C), used as the absorbing layer in these devices. Phase transitions always result in volume alterations of the crystallites, which may result in regions with loss of electrical contact between layers. In this work, photovoltaic cells based on the organometallic perovskite CH3NH3PbI3, with and without a porous layer between the perovskite and the blocking layer, were prepared and characterized. The porous layer is prepared with a TiO2 aerogel-based suspension. The behavior of these devices was evaluated in thermal cycles between 30 and 80 degrees C. With the addition of the aerogel-based layer, a significant increase of the stability of the devices was obtained after several temperature cycles.