Concept Of Intermediate Band Solar Cell Research Articles

Experimental Evidence of Complex Energy-Level Structuring in Quantum Dot Intermediate Band Solar Cells

III–V quantum dot systems are widely studied to implement the promising intermediate band solar cell concept. However, current performances are quite lower than theoretical expectations, and several loss mechanisms were proposed to explain the experimental findings. Here we show that quantum dot solar cells are far from a simple intermediate band system because of complex energy structuring. Thanks to the combination of high-quality heterostructures and high-resolution modulation spectroscopy, we experimentally unveil specific resonances, hidden upon continuous wave spectroscopy inspection because of ensemble effects and thermal broadening. These resonances are associated with strain-induced localized states and to crossed transitions and arise from the coexistence of materials with different dimensionalities (i.e., nanostructures, wetting layers, and continuum). The study clearly shows that accurate energy structuring modeling is required for these systems to be effectively considered as intermediate band solar cell solutions.

Evaluation of the efficiency potential of intermediate band solar cells based on thin-film chalcopyrite materials

This paper discusses the potential of the intermediate band solar cell (IBSC) concept to improve the efficiency of thin-film chalcopyrite solar cells. The results show that solar cells based on CuGaS2, with a radiative limiting efficiency of 46.7%, exhibit the highest potential. A simple method for the identification of transition elements that when incorporated in CuGaS2 could possibly introduce an intermediate band is also described. The IBSC concept is also applied under the assumptions that thin-film solar cells are not to be operated under concentrated light and that a non-negligible contribution of nonradiative recombination exists.

Experimental Analysis of the Operation of Quantum Dot Intermediate Band Solar Cells

With a 63.2% theoretical efficiency limit, the intermediate band solar cell (IBSC) is a new photovoltaic device proposed to overcome the 40.7% efficiency limit of conventional single gap solar cells. Quantum dot technology can be used to take the IBSC concept into practice. In this respect, the results of experiments carried out recently to characterize IBSC solar cells containing different numbers of InAs quantum dot layers as well as the theoretical models used to describe and analyze the related experimental data are summarized here. Electroluminescence and quantum efficiency measurements confirm that the main operating conditions for IBSCs are complied with in structures with a low number of QD layers. These conditions include the production of photocurrent from absorption of below band gap energy photons and the formation of distinctive quasi-Fermi levels associated with each electronic band (i.e., the conduction, valence, and intermediate bands).