Investigation on the Angle and Spectral Dependence of the Internal and the External Quantum Efficiency of Crystalline Silicon Solar Cells and Modules

To improve energy yield predictions and to fully understand the physical behavior of solar cells, it is necessary to investigate the effects caused by a change in the angle of incidence. All relevant angle-dependent effects are presented in this paper and angular correction factors are introduced. A new analytical model is presented, which includes internal reflection, free carrier absorption, and other parasitic absorption processes. The angular effects were exemplarily studied for the case of a very simple planar solar cell sample and a standard module sample. With an effective angle approach, the variation of the internal quantum efficiency in the standard solar module could be emulated and the results were verified with the help of a ray tracing tool developed for this purpose. The influence of the different angular factors on the current density of a standard module at an incidence angle of 70 degrees is finally presented

The Optical Diode Ideality Factor Enables Fast Screening of Semiconductors for Solar Cells

In the search for new materials for solar cells, a fast feedback is needed. Radiative efficiency measurements based on photoluminescence PL are the tool of choice to screen the voltage a material is capable of. Additionally the dependence of the radiative efficiency on excitation density contains information on the diode ideality factor, which determines in turn the fill factor of the solar cell. Both parameters are immediate ingredients of the efficiency of a solar cell and can be determined from PL measurements, which allow fast feedback. The method to determine the optical diode ideality factor from PL measurements and compare to electrical measurements in finished solar cells are discusse

Thin film solar cells based on the ternary compound Cu2SnS3

Alongside with Cu2ZnSnS4 and SnS, the p-type semiconductor Cu2SnS3 also consists of only Earth abundant and low-cost elements and shows comparable opto-electronic properties, with respect to Cu2ZnSnS4 and SnS, making it a promising candidate for photovoltaic applications of the future. In this work, the ternary compound has been produced via the annealing of an electrodeposited precursor in a sulfur and tin sulfide environment. The obtained absorber layer has been structurally investigated by X-ray diffraction and results indicate the crystal structure to be monoclinic. Its optical properties have been measured via photoluminescence, where an asymmetric peak at 0.95 eV has been found. The evaluation of the photoluminescence spectrum indicates a band gap of 0.93 eV which agrees well with the results from the external quantum efficiency. Furthermore, this semiconductor layer has been processed into a photovoltaic device with a power conversion efficiency of 0.54%, a short circuit current of 17.1 mA/cm2, an open circuit voltage of 104 mV hampered by a small shunt resistance, a fill factor of 30.4%, and a maximal external quantum efficiency of just less than 60%. In addition, the potential of this Cu2SnS3 absorber layer for photovoltaic applications is discussed