Influence of Surface Recombination on Open Circuit-Voltage of a Single Nanowire Solar Cell with Radial p - n Junction
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uence of Surface Recombination on Open Circuit-Voltage of a Single Nanowire Solar Cell with Radial p-n Junction S. G. Petrosyana, b, *, V. A. Khachatryana, and S. R. Nersesyanb aRussian–Armenian
University, Yerevan, Armenia Institute of Radiophysics and Electronics, NAS of Armenia, Ashtarak, Armenia *e-mail: [email protected]
b
Received February 19, 2020; revised March 30, 2020; accepted April 5, 2020
Abstract—An analytical model is proposed for the study of the effect of surface recombination on the characteristics of a solar cell made of a nanowire with a radial p-n junction formed between its ‘core’ and ‘shell’ with different types of the conductivity. The influence of the surface recombination on such important parameters of the solar cell as the short circuit current, open circuit voltage, and efficiency of conversion of the energy of solar radiation into electrical energy is considered when the shell width is varying over a wide range. It is shown that the relatively low open-circuit voltage, often observed experimentally in such solar cells, can be partially caused by significant surface recombination on the sidewall of the nanowire, the role of which increases with decreasing nanowire diameter and increasing surface to volume ratio. Keywords: nanowire, solar cell, p-n junction, surface recombination DOI: 10.3103/S1068337220030111
1. INTRODUCTION Semiconductor nanowires (NWRs) (also called whisker nanocrystals or nanorods) with a high length to diameter ratio are being currently intensively studied to create new semiconductor devices having of transverse sizes in the range from several hundred nm to microns and lengths of the order of tens of microns [1]. Such structures with a single nanowire or an array of nanowires open up new possibilities for the nanoscale integration. Due to classical size effects and the high role of surface states, they exhibit unique electrical, photoelectric and optical properties, have high biological and chemical sensitivity, and can serve as the basis for the fabrication of new photodetectors [2], third-generation solar cells (SCs) [3–5], field-effect transistors [6], biosensors [7], etc. Technological methods for the implementation of NWRs, in particular, the vapor-liquid-solid growth method, have now reached a level where, during the growth process, various layers or sections that differ in both composition and type of doping can be included in the structure of the NWR in the axial or radial directions, while forming structures with axial or radial p-n- homo (hetero)- junctions [8–10]. One of the most studied phenomena in semiconductor NPs is their high sensitivity to light, which makes NWRs promising for the use as photodetectors and other photoelectric devices [2]. Coaxial structures in which the doped core of the NWR is surrounded by a shell of the opposite type of conductivity, which leads to the appearance of a p-n (or p-i-n) junction in the radial direction, are of particular interest. The physics of the occurrence of the photocurrent (photovoltage) in such stru
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