Improving the Light Harvesting of Second Generation Solar Cells with Photochemical Upconversion

Current solar cells are fundamentally limited by their inability to harvest photons with energies less than the absorber optical threshold. Thin amp; 8208;film solar cells, usually having band gaps above the optimum single amp; 8208;threshold value of 1.34 eV given by the Shockley amp; 8208;Queisser limit, and a much smaller volume to absorb the light, are particularly prone to this loss mechanism and thus suffer from imperfect usage of the solar spectrum. An elegant way towards overcoming this limitation and using a larger fraction of the incident light is the re amp; 8208;shaping of the solar spectrum by upconversion UC of photons. In the present work we apply photochemical upconversion, as realized by triplet amp; 8208;triplet annihilation in organic molecules, to amorphous silicon thin film solar cells, incoherently transforming light from the 600 amp; 8208;750 nm to the 550 amp; 8208;600 nm wavelength range. Employing a moderate concentration of 19 suns, we demonstrate a relative gain of up to 3 in quantum efficiency around 700 nm and a relative overall efficiency increase of 0.2 . We further pinpoint a pathway which will allow significantly increasing the gain by UC and which can adapted to various single threshold devices, including organic and dye amp; 8208;sensitized solar cell

Improving the light harvesting of amorphous silicon solar cells with photochemical upconversion

Single threshold solar cells are fundamentally limited by their ability to harvest only those photons above a certain energy. Harvesting below threshold photons and re radiating this energy at a shorter wavelength would thus boost the efficiency of such devices. We report an increase in light harvesting efficiency of a hydrogenated amorphous silicon a Si H thin film solar cell due to a rear upconvertor based on sensitized triplet triplet annihilation in organic molecules. Low energy light in the range 600 750 nm is converted to 550 600 nm light due to the incoherent photochemical process. A peak efficiency enhancement of 1.0 0.2 at 720 nm is measured under irradiation equivalent to 48 3 suns AM1.5 . We discuss the pathways to be explored in adapting photochemical UC for application in various single threshold device

Photochemical Upconversion Applied to Organic and Thin Film Silicon Solar Cells

We will review triplet triplet annihilation upconversion TTA UC demonstrating a solar cell spectral response peak enhancement of 13 and a photocurrent increase of 0.28mA cm2 under moderate concentration. We will discuss the potential of TTA UC for device applicatio

Efficiency Enhancement of Organic and Thin Film Silicon Solar Cells with Photochemical Upconversion

The efficiency of thin film solar cells with large optical band gaps, such as organic bulk heterojunction or amorphous silicon solar cells, is limited by their inability to harvest the infra red part of the solar spectrum. Photochemical upconversion based on triplet amp; 8722;triplet annihilation TTA UC can potentially boost those solar cells by absorbing sub bandgap photons and coupling the upconverted light back into the solar cell in a spectral region that the cell can efficiently convert into electrical current. In the present study we augment two types of organic solar cells and one amorphous silicon a Si H solar cell with a TTA upconverter, demonstrating a solar cell photocurrent increase of up to 0.2 under a moderate concentration 19 suns . The behavior of the organic solar cells, whose augmentation with an upconverting device is so far unreported, is discussed in comparison to a Si H solar cells. Furthermore, on the basis of the TTA rate equations and optical simulations, we assess the potential of TTA UC augmented solar cells and highlight a strategy for the realization of a device relevant current increase by TTA upconversio

Dye Sensitized Solar Cell with Integrated Triplet Triplet Annihilation Upconversion System

Photon upconversion UC by triplet triplet annihilation TTA UC is employed in order to enhance the response of solar cells to sub bandgap light. Here, we present the first report of an integrated photovoltaic device, combining a dye sensitized solar cell DSC and TTA UC system. The integrated device displays enhanced current under sub bandgap illumination, resulting in a figure of merit FoM under low concentration 3 suns , which is competitive with the best values recorded to date for nonintegrated systems. Thus, we demonstrate both the compatibility of DSC and TTAUC and a viable method for device integratio