Hi group, This wednesday we will have a visiting post doc candidate, Tony Wu from the Marc Baldo group at MIT, he comes from an excitonic device background (organic photovoltaics and OLED) and is interested in materials discovery. *If you want to meet him, I have a few meeting slots available. Also lunch slots.* He will giving a talk on Wednesday, 3-4 pm Division room, titled: *Towards High Efficiency Solar Cell Utilizing Singlet Fission and Triplet-Triplet Annihilation* Abstract: Single bandgap solar cell, such as the conventional silicon solar cell, are bounded by an upper limit of 32% power conversion efficiency (PCE) due to Shockley-Queisser limit. Most of the energy losses comes from non-absorbed lower energy photons and themalization decay loss of higher energy photons. To overcome the Shockley-Queisser PCE limit, down conversion and up conversion mechanisms are some possible methods. We explored the possibility of utilizing singlet fission and triplet-triplet annihilation phenomenon in some organics for energy down conversion and up conversion. We found that internal quantum efficiency for exciton generation reaches 127% for tetracene [1]. For up conversion, the efficiency is about 0.28% [2]. Finally, we would show current progresses toward utilizing singlet fission in silicon solar cell. [1] T. Wu, et al. "Singlet fission efficiency in tetracene-based organic solar cells", APL 2014. [2] T. Wu, et al. "Solid state photon upconversion utilizing thermally activated delayed fluorescence molecules as triplet sensitizer", APL 2015. Hope all is well,