Exploring Thermochromic Behavior of Hydrated Hybrid Perovskites in Solar Cells

Highly reproducible and reversible thermochromic nature of dihydrated methylammonium lead iodide is found. A wide bandgap variation of the material (∼2 eV) is detected between room temperature and 60 °C under ambient condition as a result of phase transition caused by moisture absorption and desorption. In situ X-ray diffraction and Fourier transform infrared spectroscopy studies are performed to understand the mechanistic behavior during the phase transition. This thermochromic property is further explored as absorber material in mesostructured solar cells. Temperature-dependent reversible power conversion efficiency greater than 1% under standard test conditions is demonstrated; revealing its potential applicability in building integrated photovoltaics

On the Uniqueness of Ideality Factor and Voltage Exponent of Perovskite-Based Solar Cells

Perovskite-based solar cells have attracted much recent research interest with efficiency approaching 20%. While various combinations of material parameters and processing conditions are attempted for improved performance, there is still a lack of understanding in terms of the basic device physics and functional parameters that control the efficiency. Here we show that perovskite-based solar cells have two universal features: an ideality factor close to two and a space-charge-limited current regime. Through detailed numerical modeling, we identify the mechanisms that lead to these universal features. Our model predictions are supported by experimental results on solar cells fabricated at five different laboratories using different materials and processing conditions. Indeed, this work unravels the fundamental operation principle of perovskite-based solar cells, suggests ways to improve the eventual performance, and serves as a benchmark to which experimental results from various laboratories can be compared

Enhancing the Performance of Blade-Coated Perovskite/Silicon Tandems via Molecular Doping and Interfacial Energy Alignment

We improve the performance of blade-coated perovskite/silicon tandem solar cells using two approaches. First, we introduce F6TCNNQ as a molecular dopant in the precursor ink to enable micrometer-thick perovskite films, compatible with textured silicon bottom cells. Second, we minimize the energy mismatch between the hole selective contact and perovskite, resulting in a champion tandem efficiency of 29.7%

Unleashing the Full Power of Perovskite/Silicon Tandem Modules with Solar Trackers

Perovskite/silicon tandem photovoltaics is a promising technology to exceed the performance limit of single-junction solar cells. For utility-scale photovoltaic plants, trends and forecasts indicate that bifacial modules mounted on solar trackers will increasingly dominate the market in the next 20 years. In line with this roadmap, we investigate the outdoor performance of perovskite/silicon tandem solar cells mounted on a horizontal single-axis solar tracker in an environment with elevated solar insolation and albedo. We experimentally demonstrate in such conditions that a bifacial monolithic tandem solar cell installed on a tracker can generate 55% more power than an equivalent tandem mounted on a fixed rack. On the basis of our results, we anticipate a significant economic advantage by coupling bifacial monolithic perovskite/silicon tandem technology with solar trackers

Mechanical Reliability of Fullerene/Tin Oxide Interfaces in Monolithic Perovskite/Silicon Tandem Cells

High-efficiency perovskite-based solar cells comprise sophisticated stacks of materials which, however, often feature different thermal expansion coefficients and are only weakly bonded at their interfaces. This may raise concerns over delamination in such devices, jeopardizing their long-term stability and commercial viability. Here, we investigate the root causes of catastrophic top-contact delamination we observed in state-of-the-art p-i-n perovskite/silicon tandem solar cells. By combining macroscopic and microscopic analyses, we identify the interface between the fullerene electron transport layer and the tin oxide buffer layer at the origin of such delamination. Specifically, we find that the perovskite morphology and its roughness play a significant role in the microscopic adhesion of the top layers, as well as the film processing conditions, particularly the deposition temperature and the sputtering power. Our findings mandate the search for new interfacial linking strategies to enable mechanically strong perovskite-based solar cells, as required for commercialization

Mechanical Reliability of Fullerene/Tin Oxide Interfaces in Monolithic Perovskite/Silicon Tandem Cells

High-efficiency perovskite-based solar cells comprise sophisticated stacks of materials which, however, often feature different thermal expansion coefficients and are only weakly bonded at their interfaces. This may raise concerns over delamination in such devices, jeopardizing their long-term stability and commercial viability. Here, we investigate the root causes of catastrophic top-contact delamination we observed in state-of-the-art p-i-n perovskite/silicon tandem solar cells. By combining macroscopic and microscopic analyses, we identify the interface between the fullerene electron transport layer and the tin oxide buffer layer at the origin of such delamination. Specifically, we find that the perovskite morphology and its roughness play a significant role in the microscopic adhesion of the top layers, as well as the film processing conditions, particularly the deposition temperature and the sputtering power. Our findings mandate the search for new interfacial linking strategies to enable mechanically strong perovskite-based solar cells, as required for commercialization