Stable high voltages in solar cells can be transferred directly to modules with no losses and are becoming increasingly important. Solar cells with high voltages have lower temperature coefficients and therefore higher energy yield in PV systems, particularly for those exposed to high temperatures (e.g., in desert regions). This paper presents the optimization of a large area n-type passivated emitter rear and totally diffused rear-junction (n-PERT-RJ) solar cell to reach open-circuit voltages exceeding 690 mV and 22% stable solar cell efficiencies by using industrial diffusions and screen-printed metallization on both sides. With a free energy loss analysis and Quokka3 simulations, the recombination and resistive loss mechanisms in the n-PERT-RJ solar cells are identified and a guideline for future development is given, showing a practical roadmap toward 700 mV open-circuit voltages and solar cell efficiencies approaching 23%.

We present laser-doped interdigitated back contact (IBC) solar cells with efficiencies of 23% on an area of 244 cm² metallized by a screen-printed silver paste. Local laser doping is especially suited for processing IBC cells where a multitude of pn-junctions and base contacts lay side by side. The one-sided deposition of boron-doped precursor layers by atmospheric pressure chemical vapor deposition (APCVD) is a cost-effective method for the production of IBC cells without masking processes. The properties of the laser-doped silicon strongly depend on the precursor’s purity, thickness, and the total amount of boron dopants. Variations of the precursor in terms of thickness and boron content, and of the laser pulse energy density, can help to tailor the doping and sheet resistance. With saturation-current densities of 70 fA/cm² at sheet resistances of 60 Ohm/sq, we reached maximum efficiencies of 23% with a relatively simple, industrial process for bifacial IBC-cells, with 70% bifaciality measured on the module level. The APCVD-layers were deposited with an inline lab-type system and a metal transport belt and, therefore, may have been slightly contaminated, limiting the efficiencies when compared to thermal-diffused boron doping. The use of an industrial APCVD system with a quartz glass transport system would achieve even higher efficiencies.

As compared with the traditional back surface field (BSF) solar cells, the n-type passivated emitter rear and totally diffused rear-junction (n-PERT-RJ) solar cells have much lower carrier recombination losses on their rear sides. In order to obtain more benefits (higher open-circuit voltages) from the currently passivated rear sides, the implementation of the point contact concept is an intuitive solution. In this article, we present industrial screen-printed point contacts that are metallized with aluminum (Al) pastes containing silicon additives (Si-add). To understand the impacts of the Si-add on the performance our n-PERT-RJ solar cells, the detailed loss analysis on the open-circuit voltage (V $_{\rm OC}$ ), short-circuit current density (J $_{\rm OC}$ ), and fill factor are performed separately. The effect of Si-add and pitch of laser contact openings (LCO) on the point contact characteristics are also investigated. In the last part, we introduce an innovative “point-line” contact concept on the rear side, which is composed of dot-shaped LCO and Al metal finger design, resulting in an n-PERT-RJ solar cell to reach V $_{\rm OC}$ of 692 mV and peak efficiency of 22%. The 60% bifaciality of the device opens the way for an additional power output on module level, which further reduces the levelized cost of electricity. These features make the rear-side point contact design more flexible to be applied in industrial mass production.

We present the characterisation of directionally solidified n-type Si ingots. Three ingots with a range of bulk resistivities and different n-type doping elements (Sb, P and As) were studied. We show from Hall measurements that the mc-Si material has excellent electrical transport properties. The mobilities are close to the theoretical limit, which is given mainly by scattering at acoustical phonons. Mobilities so close to the theoretical value have, to our knowledge, not been demonstrated for comparable p-type mc-Si wafers. Additional measurements on high quality p-type mc-Si material support this statement. This means that other scattering mechanisms reduce the mobility in p-type mc-Si material, but are not present in n-type silicon. Lifetime measurements were conducted by /spl mu/W-PCD using an iodine-ethanol surface passivation. This passivation was used preferably to SiN/sub x/, as in some experiments the hydrogen from the PECVD SiN seemed to passivate the bulk at deposition temperatures. Average values in excess of 120 /spl mu/s over large areas were measured. In order to exploit the good material properties of n-type mc-Si, solar cell concepts must be developed and the processes optimised. B-diffusion is the most problematic step as it is considered to be both destructive to material quality and energy consuming. In this paper, we show that a BBr/sub 3/-emitter diffusion is possible at moderate temperatures without degrading the carrier lifetime of the mc-Si material. An additional contribution from Libal et al. on solar cell processing is included in this conference.

We report on free-induction decay measurements of nuclear spin precession of Xenon atoms confined in a small-sized vapour cell. The experiment is an important step towards the realization of a compact nuclear magnetic resonance gyroscope.

The influence of aluminum co-doping in boron-doped Cz PERC solar cells on current-induced degradation and regeneration kinetics is investigated at different injection currents and varying elevated temperatures. A carrier-induced degradation (CID) setup for simultaneous degradation and in-situ measurement was utilized for long-term treatment experiments. Different treatment conditions resulted in varying CID behavior, thus showing a significant impact on the degradation and regeneration. Evaluating the degradation and regeneration curves, kinetic rates and activation energies are determined and compared to solely boron-doped PERC cells and aluminum co-doped carrier lifetime samples.