Semiconductor Physics, Quantum Electronics & Optoelectronics. 2014. V. 17, N 1. P. 014-020.
Analysis of features of recombination mechanisms
in silicon solar cells
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
Abstract. Investigated in this paper are theoretical and experimental spectral dependences of the short-circuit current as well as small-signal photo-e.m.f. in silicon solar cells. The authors have considered two constructions of solar cells. The first construction is a solar cell with contacts on the front and back surfaces, and the second - solar cells with back barriers and contact metallization. Analyzed in the work are spectral dependences of the internal quantum efficiency for the short-circuit current and small- signal photo-e.m.f. It has been shown that the short-wave drop of the short-circuit current is related with recombination on deep centers at the front surface as well as inter-band Auger recombination in the heavily doped emitter. At the same time, availability of the short- wave drop in the small-signal photo-e.m.f. is related with limitation of the efficient rate of surface recombination Seff (λ) due to diffusion inflow. The latter takes place when a layer with the thickness dp and increased recombination is available near illuminated surface. In this case, the mechanism providing decrease in the small-signal photo-e.m.f. in the area of strong light absorption is related with increasing the efficient rate of surface recombination near the front surface, when the dominant amount of electro-hole pairs is generated in the layer with the increased recombination rate. The same mechanism is responsible for the short-circuit current drop in solar cells with back barriers and contact metallization. Juxtaposition of theoretical and experimental results enabled to determine parameters that characterize sub-surface properties of solar cells, namely: the thickness of the surface layer with increased recombination, lifetime of carriers in it, and dependences Seff (λ).
Keywords:silicon solar cell, photo-e.m.f., surface recombination.
Manuscript received 26.11.13; revised version received 00.00.13; accepted for publication 20.03.13; published online 31.03.13.