Silicon nitride nanolayers for MIS/IL solar cells
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ZAKHVALINSKII, Vasilii, PILYUK, E., GONCHAROV, I., RODRIGES, V., SIMASHKEVICH, Aleksey, SHERBAN, Dormidont, BRUC, Leonid, CURMEI, Nicolai, RUSU, Marin. Silicon nitride nanolayers for MIS/IL solar cells. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 264.
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Materials Science and Condensed Matter Physics
Editia 7, 2014
Conferința "Materials Science and Condensed Matter Physics"
7, Chișinău, Moldova, 16-19 septembrie 2014

Silicon nitride nanolayers for MIS/IL solar cells


Pag. 264-264

Zakhvalinskii Vasilii1, Pilyuk E.1, Goncharov I.1, Rodriges V.1, Simashkevich Aleksey2, Sherban Dormidont2, Bruc Leonid2, Curmei Nicolai2, Rusu Marin23
 
1 Belgorod State University,
2 Institute of Applied Physics, Academy of Sciences of Moldova,
3 Helmholtz-Centre Berlin for Materials and Energy
 
Disponibil în IBN: 16 martie 2019


Rezumat

Crystalline Si is still the mostly used material for the fabrication of solar cells (SCs). Now, the efforts of the scientists are focused on the elaboration of new types of low-cost photovoltaic (PV) devices, what could be achieved by simplifying the fabrication technology and reducing the material consumption. Different nanolayers, e.g. ITO, SiC, Si3N4 are used for the preparation of Si based SCs. Such devices are metal-insulator-Silicon (MIS) surface barrier structures with an inversion layer (IL) located in silicon near the heterojunction interface. Si3N4 was introduced for the first time into PV for the fabrication of MIS/IL solar cells as early as the 1980s. Further investigations showed that very low surface recombination velocities can be achieved using Si3N4 films in SC fabrication, while using these films also as AR coatings. Si3N4 films are mainly prepared by CVD, PECVD, electron cyclotron resonance, or reactive magnetron sputtering (RMS). Even though CVD is widely used for obtaining those films, the main disadvantages of this technique are the incorporation of H2 in the films and high substrate temperatures. The entrapped hydrogen in the films can deteriorate the properties of Si3N4 and therefore a high substrate temperature is generally undesired in microelectronic applications. Si3N4 films with extremely low hydrogen content can be prepared by RMS at a low substrate temperature. Especially promising for the deposition of Si3N4 thin films is the high-frequency non-reactive magnetron sputtering (HFNRMS) because is a non-toxic and a low material consumption deposition method. Hence, the aim of this contribution is the demonstration of the possibility to fabricate MIS/IL SCs by a simple and low-cost HFNRMS technology using Si3N4 nanolayers. Si3N4 thin films were prepared by HFNRMS in an Ar atmosphere. A previously synthesized silicon nitride was used as a solid-state target. Deposition was carried out on a cold substrate of p-Si (100) with a resistivity of 2 Ohm×cm. The layer of SiO2 was removed from the Si substrate by chemical etching in HF before Si3N4 film deposition. n-Si3N4 nanolayers with thicknesses up to 20 nm were deposited on p-Si substrates and used for the SC preparation. The results of electron diffraction investigations, obtained in a transmission electron microscope from a thin foil of a Si3N4 nanofilm, demonstrates that as-deposited Si3N4 thin films consist of a mixture of microcrystalline and amorphous phases. The control of the Si3N4 films thickness and the study of the surface morphology were performed by the method of atomic force microscopy in contact mode. The composition of deposited layers was characterized by Raman spectroscopy. SCs consisted of a substrate of p-type (100)-oriented Si crystal, covered by a mixed amorphous- nanocrystalline Si3N4 thin film. An Ag grid was deposited onto Si3N4 thin film to form the front electrode, while a continuous Cu layer was deposited on the opposite side of the Si wafer to form the rear electrode. Best SC performances were achieved on devices with Si3N4 layers with a thickness up to 20 nm. The SC devices were studied by performing dark I–V measurements and investigating spectral dependences of the SCs photo sensitivity. The barrier height at the Si/Si3N4 interface estimated from dark I-V measurements in the temperature range of 300 – 450 K varied between 0.9 eV and 1.0 eV. These values are much higher than the half of the Si band gap. Therefore we conclude that a MIS/IL type SC is obtained and that the entire space charge region, where the light absorption takes place and charge carriers are generated and separated, is located in Si. This fact is in addition confirmed by the spectral dependence of the Si/Si3N4 photo sensitivity, which entirely corresponds to the respective characteristic of Si SCs. The SC PV parameters were determined from illuminated load I-V characteristics under standard AM1.5 conditions. The short-circuit current density was 18.6 mA/cm2, the open circuit voltage 0.538 V, the fill factor 51% and the efficiency 6.38%.