We apply the publicly available device modeling tool SC-Simul for simulating experiments with user-defined heterojunction diodes to discuss the role of the electric field in solar cells. For amorphous silicon/crystalline silicon heterodiodes, the role of interface defects, an amorphous silicon buffer layer and low-cost crystalline silicon is studied by simulation of current-voltage characteristics and photoluminescence. Photoluminescence is sensitive to the minority carrier density in the volume of the device and can be used to monitor minority carrier properties in these diodes.

Detailed structural investigations have been performed on a-Si1−xGex:H in 0 ≤ x ≤ l namely Raman, X-ray Photoelectron, and Photothermal Deflection Spectroscopies, which reveal the silicon sub-matrix to be considerably more rigid than the germanium one. In Si-Ge dominated networks distinct deviations from an overall random distribution of Si and Ge atoms can be deduced from a semi-quantitative analysis of the Raman data.

Modulated primary photocurrent (MPC) studies on pin structures show spatial variations of the gap state distribution across the i-layer that can be correlated with Fermi level shifts by band bending towards interfaces. These results as well as reverse bias annealing effects are explained in terms of the defect pool model. It is demonstrated that MPC measurements are basically identical to TOF measurements with clear advantages in the post-transit time regime.

This concise primer on photovoltaic solar energy conversion invites readers to reflect on the conversion of solar light into energy at the most fundamental level and encourages newcomers to the field

The conversion of light into different types of energy is based upon the interaction of electromagnetic radiation with matter. The matter might be represented by atoms, molecules, small clusters, liquids, or solids, such as metals, semiconductors, or dielectrics, and the radiation may be formulated in the wave approach with Maxwell's equations. The light-matter interaction also may be expressed in the particle picture with Hamiltonians for each of the relevant species and by the appropriate vector potential for the radiation.

We analyze Cu(In,Ga)Se2 absorbers with a scanning near-field optical microscope (SNOM) by photoluminescence (PL). Such measurements allow one to extract local fluctuations of the integral PL yield, the quasi-Fermi level splitting, and the material composition in the submicron range. However, the experimental findings depend strongly on the surface roughness of the absorber: If the surface is rough, artifact-prone correlations between surface contour and PL features measured by SNOM can be found that complicate the study of recombination effects. For smooth surfaces, such correlations no longer exist and the influence of grain boundaries on the integral PL yield and the quasi-Fermi level splitting is revealed. The method also allows a detailed determination of the local band gaps in neighboring grains and their spatial variation inside, and thus of possibly local changes in chemical composition of different grains.

The Sun Sun is a nuclear fusion reactor with a life expectance of about 4. 5 × 109 years. In its core, at a proton density of 1025 cm−3 and a temperature of 1. 5 × 107 K, protons (p+) are converted by fusion processes and via several intermediate steps into nuclear products, such as helium (2 4He), amongst others [1]. The average energy gain per nucleon in such fusion reactions amounts to several MeV. The total rate of change of the mass deficit of the Sun amounts to $$\dot{m} = 6 \times 10^{9}\,\mathrm{kg/s}$$ , corresponding to a total power of 3. 6 × 1026 W emitted by the outer surface of the Sun, or an energy flux $$\displaystyle{\varGamma _{\epsilon,\mathit{Sun}} =\varGamma _{\epsilon }(R_{\mathrm{Sun}} = 6.9 \times 10^{8}\,\mathrm{m}) = 6 \times 10^{7}\,\mathrm{W/m}^{2}\;.}$$

The gallium gradient in Cu(In,Ga)Se-2 (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co-evaporation processes, plays a key role in the device performance of CIGS thin-film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X-ray measurements. In addition, the gallium grading of a CIGS layer grown with an in-line co-evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth-dependent occurrence of lateral inhomogeneities on the mu m scale in CIGS deposited by the co-evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi-Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross-sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper-vacancy-mediated indium and gallium diffusion in CuInSe2 and CuGaSe2 were calculated using density functional theory. The migration barrier for the In-Cu antisite in CuGaSe2 is significantly lower compared with the Ga-Cu antisite in CuInSe2, which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co-evaporation and selenization processes. Copyright (c) 2014 John Wiley & Sons, Ltd.