T. Brammer

Defect density and recombination lifetime in microcrystalline silicon absorbers of highly efficient thin-film solar cells determined by numerical device simulations

The absorber layers of microcrystalline silicon thin-film solar cells with p-i-n structure deposited by plasma-enhanced chemical vapor deposition at 200 °C are characterized regarding the defect density and the recombination lifetime. The characterization is based on a comparison of experimentally determined solar cell characteristics with results from numerical device simulations. Evaluation of the dark reverse saturation current indicates a strong dependence of the recombination lifetime τ on the hydrogen dilution during the deposition. Close to the transition region to amorphous growth, where the highest solar cell efficiencies are observed, τ is maximum within the crystalline deposition regime and equals around 80 ns. The aspect of a spatially varying defect density within the absorber layer is also addressed by numerical simulations. The results from the analysis of the dark current are compared with electron spin resonance data determined on single layers, which allows conclusions to be drawn regard...

Investigation of the optoelectronic properties of μc-Si:H pin solar cells

Abstract We have investigated microcrystalline silicon (μc-Si:H) pin solar cells deposited at different silane concentrations in the gas phase varying from 2% to 7.2%. For these cells three features were found: the dark current of the cells decreased, the open circuit voltage increased and the blue response reduced with increasing silane concentration during deposition. To study the transport and recombination of these structures we have compared the experimentally determined optoelectronic properties with simulated data. The simulations reveal that the equilibrium carrier concentration of free carriers decreases and the affect of the nucleation region of the i-layer on the blue response increases with increasing silane concentration.

Numerical analysis of the spin-dependent dark current in microcrystalline silicon solar cells

We present a detailed analysis of the voltage dependence of dangling bond recombination in microcrystalline silicon p-i-n diodes observed in the forward dark current at room temperature by electrically detected magnetic resonance (EDMR). The EDMR response is numerically simulated with physically reasonable parameters that are well suited to fully describe the electronic behavior of the diodes. A sign reversal as observed for amorphous silicon diodes is predicted at high voltages. The basic mechanism causing the sign reversal is shown to be due to space charge. The high sensitivity of the EDMR response to various material parameters is demonstrated.

Characterization of microcrystalline silicon thin-film solar cells

Absorber layers of microcrystalline silicon thin-film solar cells deposited by plasma-enhanced chemical vapor deposition are characterized regarding the product of the recombination lifetime and the mobility (/spl mu//spl tau/). The characterization is based on a comparison of experimentally determined solar cell characteristics with results from numerical device simulations. Evaluation of the voltage dependent quantum efficiency indicates a strong dependence of /spl mu//spl tau/ on the hydrogen dilution during the deposition. Close to the transition region to amorphous growth where the highest solar cell efficiencies are observed /spl mu//sub e//spl tau/ is maximum within the crystalline deposition regime and equals 2/spl middot/10/sup -7/cm/sup 2/N.