Low-temperature treated anatase TiO2 nanophotonic-structured contact design for efficient triple-cation perovskite solar cells

Abstract

We report on the preparation and optimization of low temperature (<200 °C) processed TiO2 film as an electron transport layer (ETL) for high-performance perovskite solar cells (PSCs) compatible with flexible substrates. A high-quality ETL is spin-coated from hydrothermal synthesized single-phase crystalline anatase TiO2 nanoparticles (NPs) with an average diameter of 6 ~ 10 nm. The surface of the high crystallite TiO2 NPs reveals a tendency toward interparticle necking, facilitating compact scaffolds, resulting in PSCs with high power conversion efficiencies (PCEs). The influence of low and high temperature treated TiO2 ETL on the device performance is studied. The best planar device fabricated in superstrate configuration (sup-C) exhibits a PCE of 17.1% with a JSC of 20.3 mA/cm2. The PCE can be increased by ~ 25%, up to 23%, by moving from planar architecture in sup-C to the textured solar cell in substrate configuration (sub-C). The PSC covered with a nanophotonic-structured front contact allows gaining 8% and 15% on VOC and JSC, respectively, where 2/3 of JSC gain is attributed to improved light incoupling, while the remaining 1/3 is due to increased diffraction at long wavelengths. The optical and electrical characteristics of the devices are investigated by 3D finite-domain time-domain (FDTD) and finite element method (FEM) rigorous simulations. Detailed guidelines on the nanophotonic design are provided.