Influence of nanotexturization, nanoparticles and CdTe quantum dots in the power conversion efficiency of solar cells

The synergistic utilization of nanoparticles of Au, Ag, and Au/Ag alloys, in combination with a photon capture scheme and selected thin films, has enabled the demonstration of photovoltaic structures on single-crystal silicon substrates with an efficiency of 15%. Additionally, hybrid solar cells (i.e organic/inorganic) have also been considered as a viable alternative to develop cost effective photovoltaic devices because the Schottky union between organic and inorganic materials can be formed employing low-temperatures fabrication methods. In this presentation we specifically describe a hybrid solar cell based on an ordered array of silicon nanopillars and the conductive polymer Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS). The proposed device comprises a thin layer of the aforementioned PEDOT:PSS on an array of silicon nanopillars that was formed utilizing electroless metal-assisted-chemical-etching methods. The performance characteristics of the produced solar cells was analyized in function of the height of said nanopillars. A maximum power conversion efficiency of 9.65% was observed for an optimized height of 400 nm, even without the utilization of antireflecting films on the front surface. The effect of ultrathin films of aluminum oxide (Al₂O₃) realized employing an atomic layer deposition tool was also included in this study and its utilization further increased the measured efficiency to 10.56%. Finally, with the specific aim of lowering the cost of solar cell manufacturing, additional tests have been carried out on structures with a total thickness of less than 20 μm in which the efficiency was observed to reach 7.7% when used in conjunction with multi-spiked nanoparticles of Au/Ag alloys. The utilization of CdTe quantum dots [1-3] on nanotexturized, relatively thin samples (150 μm) has permitted achieving an efficiency of 15%. Thus, the structures discussed in this presentation are considered pro- ising towards the realization of high efficiency solar cells.