A passivating contact concept compatible with a short thermal treatment

In this study we present a boron-doped silicon carbide layers as a hole-selective contact which is compatible with short annealing time (typically < 1 minute) as the one used for firing of metal pastes. The application of such layers on symmetrically processed test structures lead to implied open circuit voltages up to 715 mV and contact resistances below 75 m Omega.cm(2). Proof-of-concept p-type solar cells employing such passivating contact stack over the full-rear side and a POCl3 diffused emitter metallized with firing-through of Ag-paste were processed, leading to a first conversion efficiency of 21.4%

Phosphorous-Doped Silicon Carbide as Front-Side Full-Area Passivating Contact for Double-Side Contacted c-Si Solar Cells

We present an electron selective passivating contact based on a tunneling SiOx capped with a phosphorous doped siliconcarbideandpreparedwithahigh-temperaturethermalanneal. We investigate in detail the effects of the preparation conditions of theSiCx(n)(i.e.,gasflowprecursorandannealingtemperature)on the interface recombination rate, dopant in-diffusion, and optical properties using test structures and solar cells. On test structures, our investigation reveals that the samples annealed at temperatures of 800–850 °C exhibit an increased surface passivation toward higher gas flow ratio (r = CH4/(SiH4 + CH4)). On textured and planar samples, we obtained best implied open-circuit voltages (i-VOC) of 737 and 746 mV, respectively, with corresponding dark saturation current densities (J0) of∼8 and∼4 fA/cm2. The SiCx(n)layerswithdifferentrvalueswereappliedonthetextured front side of p-type c-Si solar cells in combination with a borondoped SiCx(p) as rear hole selective passivating contact. Our cell results show a tradeoff between VOC and short-circuit current density (JSC) dictated by the C-content in the front-side SiCx(n). On p-type wafers, best VOC = 706 mV, FF = 80.2%, and JSC = 38.0 mA/cm2 with a final conversion efficiency of 21.5% are demonstrated for 2 × 2 cm 2 screen-printed cells, with a simple and patterning-free process based on plasma depositions and one annealing step 800 °C < T < 850 °C for the formation of both passivating contacts

Silicon Heterojunction Solar Cells on Quasi-mono Wafers

We applied hydrogen passivation, gettering and a combination of both to quasi-mono (qm) wafer material to enhance its bulk lifetime and prepared silicon heterojunction (SHJ) solar cells. We find that while our applied hydrogen passivation alone seems not to enhance lifetime, a gettering treatment increases bulk lifetime so that efficiencies up to 21.5% were achieved with a SHJ solar cell. This is close to the highest efficiency reported for such a cell. We find that the variation of the absorber thickness plays a minor role for the investigated solar cells and that similar efficiencies could have been obtained for Cz and gettered qm wafers. The latter is mainly due to the fact that the higher efficiency potential of the Cz material could not be fully exploited due to a degradation of surface passivation during the sputtering of the TCO on the cell, which could not be fully recovered in the final annealing step

A passivating contact for silicon solar cells formed during a single firing thermal annealing

Passivating contacts are indispensable for achieving high conversion efficiency in crystalline-silicon solar cells. Their realization and integration into a convenient process flow have become crucial research objectives. Here, we report an alternative passivating contact that is formed in a single post-deposition annealing step called 'firing', an essential step for current solar cell manufacturing. As firing is a fast (750 degrees C) anneal, the required microstructural and electrical properties of the passivating contact are stringent. We demonstrate that tuning the carbon content of boron-doped silicon-based thin films inhibits firing-induced layer delamination without preventing a partial crystallization. The latter promotes charge-carrier selectivity, even in the absence of a diffused doped region beyond the oxide, by inducing hole accumulation near the wafer surface. We fabricated proof-of-concept solar cells employing the developed technology, demonstrating an open circuit voltage of 698 mV and an efficiency of 21.9%, and show how it could be a drop-in replacement for today's rear contacts based on locally opened dielectric passivation stacks