From Event: SPIE Organic Photonics + Electronics, 2017
We have deposited perovskite solar cells with a bandgap of 1.68 eV onto heterojunction silicon solar cells that by themselves have an efficiency of 21% to create a 1 square centimeter monolithic tandem solar cell with an efficiency of 25.3%. We have also made all-perovskite tandems using a new ABX3 perovskite composition containing a mixture of tin and lead on the B site that have greater than 20% efficiency. With solar cells packaged between two sheets of glass with rubber edge seals, we have passed the industry standard 1000 hour 85°C 85% humidity damp heat test as well as 200 cycles between 85°C and -40°C. One of the keys to obtaining high efficiency and stability was optimizing the composition of cesium and formamidinium on the A site and iodine and bromine on the X site. We will show how light -induced phase separation occurs when there is too much bromine in the films. Another crucial step towards improving stability is the use of atomic layer deposition to deposit a tin oxide buffer layer on the perovskite that enables the sputter deposition of an indium tin oxide transparent electrode. ITO is less reactive with perovskites than the metals that are typically used in perovskite solar cells. The ALD layer has minimal parasitic absorption and prevents shunting. Our progress towards achieving 30% power conversion efficiency and passing even more aggressive stability tests will be presented.
Michael D. McGehee, "Perovskite tandem solar cells with greater than 25% efficiency and enhanced stability (Conference Presentation)," Proc. SPIE 10363, Organic, Hybrid, and Perovskite Photovoltaics XVIII, 103630N (Presented at SPIE Organic Photonics + Electronics: August 09, 2017; Published: 19 September 2017); https://doi.org/10.1117/12.2273043.5581137560001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon