3-D optical modeling of single and multi-junction thin-film silicon solar cells on gratings
- PDF / 759,688 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 46 Downloads / 196 Views
3-D optical modeling of single and multi-junction thin-film silicon solar cells on gratings O. Isabella1, S. Solntsev1, D. Caratelli2, and M. Zeman1 1 Delft University of Technology – PVMD/DIMES, P.O. Box 5053, 2628 CD Delft, Netherlands 2 Delft University of Technology – IRCTR, P.O. Box 5031, 2600 GA Delft, Netherlands ABSTRACT Three-dimensional (3-D) optical modeling based on Finite Element Method of single, double, and triple junction thin-film silicon solar cells is presented. The combination of front periodic gratings with optimal geometrical parameters and rear ZnO/Ag reflector constitutes an efficient light trapping scheme for solar cells in superstrate (pin) configuration. The application of optimized trapezoidal 1-D and 2-D gratings resulted in 25.5% (1-D case) and 32.5% (2-D case) increase in photo-current density with respect to the flat solar cell. The application of inverted pyramidal 2-D gratings in double and triple junction silicon solar cells with very thin absorber layers resulted in a photo-current density > 11 mA/cm2 and > 9 mA/cm2, respectively. INTRODUCTION Light management in thin-film silicon solar cells that aims at the enhancement of photocurrent density is crucial to achieve high conversion efficiency [1]. One of the most successful light management techniques is the light trapping, which utilizes front side texturing (antireflective and light scattering effects) and reflection at the rear side. State-of-the-art solar cells use random front textures, usually present on the surfaces of front transparent conductive oxides (TCO). Recently, another approach for front textures based on periodic gratings has been introduced and investigated. This approach proved to be a viable approach for light scattering in both pin [2, 3, 4] and nip [5, 6, 7] single and double junction thin-film silicon solar cells [8, 9]. As noted in [4], while random textures scatter light continuously in different angles, as a result of light coupling in both guided and radiation modes, periodic gratings scatter light only in discrete angles because light coupling in this case is allowed only at specific energies. This effect can be manipulated by varying gratings geometry (period, height, duty cycle), controlling the growth of materials on gratings (levelling effect [10]), and choosing materials involved in gratings-based solar cell [11]. Multi-dimensional optical modelling has become an important tool for an optimal design of multi-junction solar cells based on periodic gratings. Finite Element Method (FEM) is one of the techniques to solve numerically Maxwell equations. Recently, it has been demonstrated that two- and three-dimensional (2-D and 3-D) FEM modeling [12, 13] is an effective way to investigate thin-film silicon solar cells on 1-D and 2-D gratings in both nip and pin configurations. The unit cell of a solar cell structure with materials and thicknesses, boundary conditions and excitations have to be defined. Results of the simulations are the structure’s total reflectance and absorptance in the individual lay
Data Loading...
