New laser-based approaches to improve the passivation and rear contact quality in high effiency crystalline silicon solar cells

Laser processing has been the tool of choice last years to develop improved concepts in contact formation for high efficiency crystalline silicon (c-Si) solar cells. New concepts based on standard laser fired contacts (LFC) or advanced laser doping (LD) techniques are optimal solutions for both the front and back contacts of a number of structures with growing interest in the c-Si PV industry. Nowadays, substantial efforts are underway to optimize these processes in order to be applied industrially in high efficiency concepts. However a critical issue in these devices is that, most of them, demand a very low thermal input during the fabrication sequence and a minimal damage of the structure during the laser irradiation process. Keeping these two objectives in mind, in this work we discuss the possibility of using laser-based processes to contact the rear side of silicon heterojunction (SHJ) solar cells in an approach fully compatible with the low temperature processing associated to these devices. First we discuss the possibility of using standard LFC techniques in the fabrication of SHJ cells on p-type substrates, studying in detail the effect of the laser wavelength on the contact quality. Secondly, we present an alternative strategy bearing in mind that a real challenge in the rear contact formation is to reduce the damage induced by the laser irradiation. This new approach is based on local laser doping techniques previously developed by our groups, to contact the rear side of p-type c-Si solar cells by means of laser processing before rear metallization of dielectric stacks containing Al2O3. In this work we demonstrate the possibility of using this new approach in SHJ cells with a distinct advantage over other standard LFC techniques.

Improving the compilation of prolog to C using type and determinism information: Preliminary results

We describe the current status of and provide preliminary performance results for a compiler of Prolog to C. The compiler is novel in that it is designed to accept different kinds of high-level information (typically obtained via an analysis of the initial Prolog program and expressed in a standardized language of assertions) and use this information to optimize the resulting C code, which is then further processed by an off-the-shelf C compiler. The basic translation process used essentially mimics an unfolding of a C-coded bytecode emúlator with respect to the particular bytecode corresponding to the Prolog program. Optimizations are then applied to this unfolded program. This is facilitated by a more flexible design of the bytecode instructions and their lower-level components. This approach allows reusing a sizable amount of the machinery of the bytecode emulator: ancillary pieces of C code, data definitions, memory management routines and áreas, etc., as well as mixing bytecode emulated code with natively compiled code in a relatively straightforward way We report on the performance of programs compiled by the current versión of the system, both with and without analysis information.