Effects of bulk and grain boundary recombination on the efficiency of columnar-grained crystalline silicon film solar cells

摘要

Columnar-grained polycrystalline silicon films deposited atudlow temperatures are promising materials for use in thin-filmudphotovoltaics. We study the effects of recombinationudat grain boundaries, bulk intragranular recombination,udgrain size, and doping in such structures with two-dimensionaluddevice physics simulations, explicitlyudmodeling the full statistics and electrostatics of traps at theudgrain boundary. We characterize the transition from grain-boundary-limited to bulk-lifetime-limited performance as audfunction of intergranular defect density and find that higherudbulk lifetimes amplify grain boundary recombination effectsudin the intermediate regime of this transition. However,udlonger bulk lifetimes ultimately yield higher efficiencies.udAdditionally, heavier base doping is found to makeudperformance less sensitive to grain boundary defectuddensity.