Self-Assembled Multilayers to Enhance Photon Upconversion and Solar Cell Efficiency

Photon upconversion (UC), combining two lower energy photons to generate a higher energy excited state, can be used to harness "sub-band gap photons" and reach maximum theoretical solar cell efficiencies of >40%. Molecular photon upconversion, by way of triplet-triplet annihilation (TTA-UC), is particularly appealing because UC is achievable even under low intensity, non-coherent, solar irradiation. Current efforts to harness TTA-UC in solar energy conversion are predominantly based on using UC solution or polymer film as a filter or reflector working in conjunction with a conventional solar cell but increase the cost and complexity of the device.

Our technology is capable of facilitating photon upconversion in films of self-assembled bilayers, presented in Tech ID 15-001. The films can be prepared by a step-wise soaking/loading procedure that is amenable to roll-to-roll printing for large scale manufacturing of devices. The self-assembled bilayer strategy is effective at facilitating photocurrent generation from the upconverted state. This technology offers a new class of self-assembled UC solar cells that show promise as a means of passing the maximum theoretical limit for single junction solar cells.