Desenvolvimento e comparação de células solares P+NN+ com emissor seletivo e homogêneo

Abstract

The solar cell industry is based on manufacturing n+pp+ devices with phosphorus emitter and aluminum back surface field. Studies show that the exposure to solar radiation may cause the degradation of electrical characteristics of these devices, which does not occur in solar cells made with n-type silicon. Furthermore, ntype silicon has a highest minority carrier lifetime and it is less sensitive to the presence of impurities when compared to p-type substrates. With the goal of the development of p+nn+ solar cells, experimental manufacturing processes were carried out to produce devices with homogeneous emitter, obtained from BBr3 and spin-on dopant, selective emitter formed by laser radiation and deposition of the antireflection coating (AR) by evaporation and atmospheric pressure chemical vapor deposition (APCVD). In solar cells with homogeneous emitter formed by BBr3 and oxidation followed by annealing at 400 °C with form ing gas provides a minimum surface passivation. It was observed that the electrical characteristics of the solar cells manufactured in n-type solar grade silicon are highly affected by the number of high-temperature thermal steps. The maximum efficiency of solar cells with emitter formed by BBr3 was 12.7%. The open circuit voltage values of solar cells with selective emitter were less than 560 mV, indicating that deterioration of the melting region by the laser radiation occurs, and the best solar cell achieved 11.6% efficiency. In general, devices with homogeneous emitter formed by spin-on showed higher efficiencies compared to the others, reaching 14.3% for solar cells with front grid formed with the PV3N1 metal paste. The TiO2 AR coatings deposited by APCVD and with the annealing at temperature of 400 °C res ults in surface passivation, increasing the efficiency of the devices to 0.5% (absolute), which does not occur in AR coatings deposited by evaporation.