Light harvesting and effective surface passivation using electrodeposited Y2O3 for broadband absorption enhancement in silicon solar cells

This paper reports investigation on passivation properties of electrodeposited yttrium oxide Y2O3 thin films on monocrystalline silicon substrate. We examined its application as an effective light harvesting and a passivation layer to enhance the electrical properties of the processed solar cell. We found that the deposited Y2O3 thin film is excellent antireflection coating and post deposition sintering acts to passivate the coated monocrystalline silicon substrate. Next, the coated substrates were annealed at various temperatures for a short duration. The crystallinity of the deposited yttrium oxide thin film was analyzed by means of X-ray diffraction. The latter shows an obvious dependence with the annealing temperature. Surface morphology was examined by a field emission scanning electron microscope and revealed a high tendency for light scattering through its particular morphology, essentially after post-annealing at 650 °C. The effective minority carrier lifetime measurements, using a WTC-120 photoconductance lifetime tester, show an obvious increase indicating the vital role of yttrium oxide on the passivation of the front surface. The electrical properties were studied using the Hall effect and the Van Der Pauw methods to measure the resistivity and mobility of the majority carriers. The effect of the deposited thin film on the optoelectronic properties was evaluated by means of the internal quantum efficiency that was improved noticeably, proving a large decrease of the recombination activities mainly at the front surface. These results show clearly that the deposited layer has a double effect: a passivating layer and an antireflective layer increasing the light trapping at the front side of the processed silicon solar cell.