DEVELOPING EFFICIENT PEROVSKITE SOLAR MODULES

Halide perovskites have attracted considerable attention due to unprecedented properties not seen in traditional semiconductors. The record efficiency of small perovskite cells is already approaching that of the best silicon crystal solar cells. However, the large area module efficiencies are lagging behind. In this dissertation, we focus on developing efficient perovskite solar modules. The introduction in Chapter 1 is adapted from my paper in the International Journal of Extreme Manufacturing.1Perovskite materials are good candidates for flexible photovoltaic applications due to their strong absorption and low-temperature processing. We demonstrate a record efficiency flexible perovskite solar module by blade coating high-quality perovskite films on flexible Corning® Willow® Glass using additive engineering. Ammonium chloride (NH4Cl) is added to the perovskite precursor solution to retard the nucleation, which prevents the voids at the interface of perovskite and glass. The implementation of NH4Cl enabled fabricating of single junction flexible perovskite solar devices with an efficiency of 19.72% on the small area cells and a record aperture efficiency of 15.86% on the modules with an area of 42.9 cm2 The content in this section is adapted from my publication in Advanced Energy Materials.2Then, we developed perovskite-only tandem modules has the potential to make breakthrough efficiencies by harvesting more sunlight. Due to the high voltage and low current density, the tandem structure intrinsically has low resistive losses when enlarging to modules. We developed a hot-gas assisted blade coating strategy that enables the fabrication of high-quality thick narrow bandgap films for making tandem modules. A reducing agent was applied to the film to overcome the oxidation during laser scribing in air. Eventually, we demonstrate perovskite-only tandem solar modules with efficiency above 21.0%. This content is adapted from a paper being accepted for publication in Nature Energy.3Besides improving the quality of each functional layer, developing high performance perovskite solar modules requires multi-factor redesigning to reduce the cell-to-module derate. We built a comprehensive model to calculate the various cell-to-module power losses. The model has been validated by experiments and shows a better than 97% precision in predicting the module efficiencies. Using this model, we identified the pathways to increase module efficiencies. The content of this part is adapted from my previous publication in PRX Energy.4The perovskite solar devices are attractive for space applications due to their remarkable power-per-weight. Also, the absence of oxygen and moisture in space favors the perovskite material. Therefore, for the application of perovskite solar modules, we studied the degradation mechanism of perovskite solar devices under intense X-ray radiation, which is one of the main radiations in space. We demonstrate that the X-ray-induced damage was attributed to the displacement of I-, creating lattice defects by the radiation-generated secondary electrons. We also studied the evolution in the spatial distribution of trap densities under X-ray radiation, which revealed that the defect-abundant perovskite/PTAA interface was the most rapidly degraded site in PSCs. This work is adapted from a manuscript being accepted for publication in IEEE Transactions on Nuclear Science.5