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June 05, 2012

Hybrid Silicon Nanocone-Polymer Solar Cells

Nanoletters - Hybrid Silicon Nanocone−Polymer Solar Cells (6 pages)

Recently, hybrid Si/organic solar cells have been studied for low-cost Si photovoltaic devices because the Schottky junction between the Si and organic material can be formed by solution processes at a low temperature. In this study, we demonstrate a hybrid solar cell composed of Si nanocones and conductive polymer. The optimal nanocone structure with an aspect ratio (height/diameter of a nanocone) less than two allowed for conformal polymer surface coverage via spin-coating while also providing both excellent antireflection and light trapping properties. The uniform heterojunction over the nanocones with enhanced light absorption resulted in a power conversion efficiency above 11%. Based on our simulation study, the optimal nanocone structures for a 10 μm thick Si solar cell can achieve a short-circuit current density, up to 39.1 mA/cm2, which is very close to the theoretical limit. With very thin material and inexpensive processing, hybrid Si nanocone/polymer solar cells are promising as an economically viable alternative energy solution.






In conclusion, we demonstrated a hybrid Si nanocone/ polymer solar cell with a power conversion efficiency of 11.1%, which is the highest among hybrid Si/organic solar cells to our knowledge. The conductive polymer, PEDOT:PSS, made a Schottky junction with Si to extract light-generated charge carriers while passivating the Si surface. This junction was formed by a simple solution-processed method at a temperature as low as 120 °C. Based on our simulation study about light absorption, the optimum nanocone structures for a thinfilm Si solar cell need to have their aspect ratios around one. This structure is well-suited for the hybrid Si/polymer solar cell since it allows for conformal polymer coating.

4 pages of supporting material

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