Suppression of hot carriers by nanoporous silicon for improved operation of a solar cell

Abstract

The surface of a silicon solar cell is modified to improve its photovoltaic characteristics. Nanostructured porous silicon layer is formed on a front n +-type surface of a p-n junction by means of electrochemical etching accompanied by illumination with a high-power light-emitting diode operating at the wavelength of 365 nm. Addition of the porous layer results in considerable increase in the capacitive photovoltage across the p-n junction. This increase is shown to be stipulated by reduced photonic losses due to anti-reflection coating effect of the porous layer, as well as by decreasing adverse effect of hot carriers on the photovoltage. Broadening of the spectrum of capacitive photovoltage towards the short-wavelength region was observed. This finding is associated with the gradedgap character of the porous layer and photovoltage formation across it as well as with increased absorption of high-energy photons in the porous layer and resulting weaker heating of free carriers.

Investigation and application of hot carrier phenomenon in photovoltaics

“…This chapter presents an experimental investigation of the hot carrier effect, focusing on the methodologies and techniques described in the Second Chapter. By using the prepared samples, precise optical excitation, temperature control, and modelling methods, the chapter gives an explanation of the behaviour of carriers with excess energy and their impact on the output signal of PV devices (Ašmontas, Fedorenko et al, 2020;Masalskyi, Gradauskas, Ašmontas et al, 2022a;Masalskyi & Gradauskas, 2021b. The acquired knowledge from such investigations guides the development of novel device structures and optimisation strategies to minimise losses caused by hot carriers.…”

“…The methodology of the dissertation consists of two main parts: theoretical modelling and experimental research (Ašmontas, Fedorenko et al, 2020;Masalskyi, Gradauskas, Ašmontas et al, 2022b;Masalskyi & Gradauskas, 2021b. Theoretical methods consist of the separation of photovoltage signal components by the programming environment MatLab, and the modelling of novel PV structures is made by 1D Poisson for PC.…”

“…Structures are analysed in which hot carriers were studied. This chapter concludes by the formulated main objective and tasks of the investigation (Ašmontas, Fedorenko et al, 2020;Gradauskas, Ašmontas, Sužiedėlis, Šilėnas, Čerškus et al, 2020b;Masalskyi, Gradauskas, Ašmontas et al, 2022a;Masalskyi & Gradauskas, 2021a.…”

“…The electrochemical etching of the Si surface was carried out in a transparent electrochemical cell with a Pt gauze electrode (Fig. 2.3b) (Ašmontas, Fedorenko et al, 2020). The fabrication was carried out at V. E. Lashkaryov Institute of Semiconductor Physics, National Academy of Science, Ukraine.…”

“…To investigate the suppression of the hot carrier impact, the porous layer was formed on the front side of the Si photodiodes; the structures were illuminated with the light of 8000 W/cm 2 intensity and of wavelength range 400-1200 nm (Ašmontas, Fedorenko et al, 2020). Results in Fig.…”