TiO2 quantum dots as superb compact block layers for high-performance CH3NH3PbI3 perovskite solar cells with an efficiency of 16.97%

A compact TiO2 layer is crucial to achieve high-efficiency perovskite solar cells. In this study, we developed a facile, low-cost and efficient method to fabricate a pinhole-free and ultrathin blocking layer based on highly crystallized TiO2 quantum dots (QDs) with an average diameter of 3.6 nm. The surface morphology of the blocking layer and the photoelectric performance of the perovskite solar cells were investigated by spin-coating with three different materials: colloidal TiO2 QDs, titanium precursor solution, and aqueous TiCl4. Among these three treatments, the perovskite solar cell based on the TiO2 QD compact layer offered the highest power conversion efficiency (PCE) of 16.97% with a photocurrent density of 22.48 mA cm(-2), a photovoltage of 1.063 V and a fill factor of 0.71. The enhancement of PCE mainly stems from the small series resistance and the large shunt resistance of the TiO2 QD layer.