Optical Simulations To Inform The Design Of Uv-Absorbing Organic Materials And Solar Cells

Organic solar cells are ideal for semi-transparent applications given their "peaky" absorption, which allows them to selectively absorb photons outside the visible range while transmitting visible light. Such devices embody a fundamental tradeoff between transparency and power generation that must be optimized to fit the requirements of each potential application-for example, powering electrically dimmable smart windows. To inform the design of organic ultraviolet-absorbers and solar cells that target such applications, we computer-generate sets of optical constants with a range of absorption coefficients and absorption cutoff wavelengths that mimic those of real organic semiconductors. We then perform optical transfer-matrix simulations to determine the absorption and transmission spectra of full-stack photovoltaic cells, inserting these computer-generated optical constants to describe the photoactive absorbing layers. We find that solar cells having absorbers with a cutoff wavelength of 420 nm produce the most power without degrading transparency or color neutrality, and that absorption coefficients up to 5 x 105 cm 1 are needed to fully absorb the targeted wavelengths within practical photoactive layer thicknesses <300 nm in the absence of a reflecting electrode.