Abstract
To get enhanced long-wavelength absorption, an impurity photovoltaic (IPV) mechanism was implemented within a transparent conducting oxide (TCO) at the rear of a solar cell. The numerical simulation of the N+/P (silicon)/IPV-TCO device was carried out by using SCAPS-1D program which allows the inclusion of optically active defects. In the proposed heterostructure configuration, ZnTe is a suitable material as back surface reflector. In analyzing the Si/ZnTe interface, lattice mismatch, energy band alignment and defects density were considered with appropriate treatment. In particular, to cure the detrimental 12% lattice mismatch at the interface, a thin silicon amorphous layer was inserted in-between, allowing 22.98% conversion efficiency. With adapted ZnTe Lucovsky's model for the optical capture cross sections and introduction of an oxygen radiative IPV defect (O2 level at 0.4 eV below the conduction band), a conversion efficiency of 27.15% was ultimately achieved. The experimental feasibility of the high-efficiency heterostructure device is evaluated.
Highlights
The stagnation of the conversion efficiency of siliconbased solar cells for more than two decades has led to the search for new concepts and adapted materials
One of the first tasks to undertake in our study will be to manage the lattice mismatch and the energy band alignment between the two adjacent materials. We report in this contribution, the numerical analysis of n+/p/p+ Si solar cells with particular emphasis on the p+ back ZnTe layer hosting an impurity photovoltaic (IPV) defect and discuss the results comparatively with those obtained with a conventional silicon solar cell
The short circuit current increase is a consequence of the quantum efficiency expansion, noticeable in the 900–1400 nm range through the IPV effect (Figure 2)
Summary
The stagnation of the conversion efficiency of siliconbased solar cells for more than two decades has led to the search for new concepts and adapted materials. The problems associated with the conventional IPV effect in the silicon substrate are related to new recombination paths while introducing states in the band gap and parasitic absorption To overcome these issues, one can consider the possibility of isolating the impurity level within a larger bandgap material located at the backside of the cell. With a direct bandgap of ∼ 2.26 eV with a zinc-blend crystal structure, ZnTe exhibits a high p-type electrical conductivity with controllable hole concentration as high as 1020 cm−3 when doped with nitrogen [12] If this latter property is compliant with expected efficiency improvement as BSF, ZnTe wide bandgap with a low electron affinity value (3.53 eV) is not a priori a suitable partner material with silicon. At the end of the study, the possibilities of technological implementation of the new structure are discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
