Resumo Células solares com emissor e face posterior passivada (PERC, passivated emitter and rear cell) vêm dominando o mercado fotovoltaico em razão de seu processo de fabricação ser compatível com as linhas industriais que vinham sendo utilizadas e pela produção de dispositivos de alta eficiência. Atualmente o silício tipo p é o mais utilizado pela indústria de células solares, mas o silício tipo n deve ganhar mercado nos próximos anos juntamente com o emprego de lâminas de espessura reduzida. O objetivo deste trabalho é apresentar uma revisão sistemática dos principais estudos na área de células solares base n, sendo elas do tipo PERC, PERT (passivated emitter-rear totally diffused) e TOPCon (tunnel oxide passivated contact), com ênfase para a abordagem de contatos seletivos, emissores seletivos e nos processos utilizados, bem como na análise de células solares de espessura reduzida em relação ao padrão da indústria atual.

Abstract The PERC (passivated emitter and rear cell) solar cells have been dominating the competitive photovoltaic market due to their manufacturing process being compatible with the industrial lines that were being used and to produce high efficiency devices. Currently, p-type silicon is the most used by the solar cell industry, but n-type silicon should gain market in the coming years along with the use of thinner wafers. This work is a systematic review that aims to find the main recent studies in the field of n-type solar cells, like PERC, PERT (passivated emitter-rear totally diffused), and TOPCon (tunnel oxide passivated contact), with emphasis on the selective contacts and selective emitters and the processes to obtain them, as well as the analysis of solar cells of reduced thickness in relation to the current industrial standard.

Spinal cord injury (SCI) is a disabling condition resulting in deficits of sensory and motor functions, and has no effective treatment. Considering that protocols with stem cell transplantation and treadmill training have shown promising results, the present study evaluated the effectiveness of stem cells from human exfoliated deciduous teeth (SHEDs) transplantation combined with treadmill training in rats with experimental spinal cord injury. Fifty-four Wistar rats were spinalized using NYU impactor. The rats were randomly distributed into 5 groups: Sham (laminectomy with no SCI, n=10); SCI (laminectomy followed by SCI, n=12); SHEDs (SCI treated with SHEDs, n=11); TT (SCI treated with treadmill training, n=11); SHEDs+TT (SCI treated with SHEDs and treadmill training; n=10). Treatment with SHEDs alone or in combination with treadmill training promoted functional recovery, reaching scores of 15 and 14, respectively, in the BBB scale, being different from the SCI group, which reached 11. SHEDs treatment was able to reduce the cystic cavity area and glial scar, increase neurofilament. Treadmill training alone had no functional effectiveness or tissue effects. In a second experiment, the SHEDs transplantation reduced the TNF-α levels in the cord tissue measured 6 h after the injury. Contrary to our hypothesis, treadmill training either alone or in combination, caused no functional improvement. However, SHEDs showed to be neuroprotective, by the reduction of TNF-α levels, the cystic cavity and the glial scar associated with the improvement of motor function after SCI. These results provide evidence that grafted SHEDs might be an effective therapy to spinal cord lesions, with possible anti-inflammatory action.