Insight into conduction band density of states at c-Si/TiO2 interface for efficient heterojunction solar cell

Abstract

Carrier selective solar cell has become one of the hot spots in the area of Si solar cell. The proposed architecture FTO/TiO2/c-Si/i-a-Si:H/Cu2O/back contact studied through simulation demonstrates a power conversion efficiency of 20.03%. This study is the first to report detailed exploration of effect of the conduction band density of states on the efficiency of Si solar cell. Through optimization, the conduction band density of state (1017 cm-3) drastically increases the power conversion efficiency from 18% (at 1021 cm-3) to 21.25% (at 1017 cm-3) i.e., an improvement of 18% relatively. Along with this, the parameters like absorber layer thickness, absorber’s defect density, thickness of electron transport layer and interface defect density are also optimized. Moreover, the charge transport properties and the impact of the Schottky barrier height at c-Si/TiO2 interface on band alignment is studied. After optimization of various physical parameters such as thickness (100 μm), conduction band density of states (1017 cm-3) and defect concentration (1010 cm−3) of c-Si layer, thickness of TiO2 layer (20 nm) and interface defect density at c-Si/TiO2 junction (1010 cm−2), a short-circuit current of 38.11 mA cm−2, open-circuit voltage of 0.84 V, fill factor of 85.99% is obtained, leading to an enhanced theoretical power conversion efficiency of 27.77%.