We report on electroluminescence (EL) imaging of organic photovoltaic cells and modules with poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester as semiconductor layer. The dominant EL emission is found in a spectral regime between 1200 and 1400 nm and is identified as the radiative decay of the charge transfer complex formed between the polymer and the fullerene. Electroluminescence emission from the pristine compounds is either much weaker or completely absent. Overall, electroluminescence imaging is shown to give valuable information on the defects but also on the performance of organic solar modules.

The reciprocity theorem for solar cell predicts a linear relation between electroluminescence emission and photovoltaic quantum efficiency and an exponential dependence of the electroluminescence signal on the applied voltage. Both dependencies are experimentally verified for polymer based solar cells in this paper. Furthermore it is shown, that electroluminescence imaging of organic solar cells has the potential to visualize the photocurrent distribution significantly faster than standard laser beam induced current mapping (LBIC) techniques.

A monocrystalline silicon wafer with a porous Si surface is an ideal seed for the epitaxial growth of thin monocrystalline Si films. After growth, we process a solar cell into the epitaxial film without using costly photolithography. We glue the cell to a glass carrier and separate it from the growth substrate at the porous Si layer. The substrate wafer is re-usable. We achieve an independently confirmed power conversion efficiency of 15.4% with a 25.5 µm-thick cell (3.88 cm 2 ) using layer transfer with porous Si.

We fabricate a 25.5‐μm‐thick monocrystalline Si solar cell with a confirmed power conversion efficiency of 15.4% and an area of 3.88 cm2 using a layer transfer process with porous Si. The process is free of photolithography and contains no high‐temperature oxidation steps. We investigate three design features that improve the short‐circuit current density to a value of 32.7 mA/cm2 under AM1.5 illumination. The detached back reflector contributes 2 mA/cm2, a reduced front‐surface reflectance accounts for an additional 2 mA/cm2 and a reduced base doping increases the current density by 1 mA/cm2. Copyright © 2002 John Wiley & Sons, Ltd.

We have fabricated a textured monocrystalline Si solar cell with a thickness of 15Á5 lm and a con®rmed ef®ciency of 12Á2% using porous silicon (PSI) for layer transfer. The PSI process avoids photolithography and high-temperature oxidation. The cell has a surface that is textured with randomly positioned inverted pyramids for light trapping. The device does not yet fully exploit the light-trapping capability of this ®lm shape, owing to a small back-surface re¯ectance.