High efficiency Si quantum dot heterojunction solar cells using a single SiO_X:B layer

Abstract

Most of the Si quantum dot (QD) has been fabricated from SiO2/SiOx multilayer structure in order to create a homogeneous size. However, this structure achieved much lower efficiencies than expected in the Si QD photovoltaic field. It is because the Si QD generation and the photoexcited carrier transport is restricted by adjacent SiO2 layer. In this study, we applied a single SiOx:B layer fabrication method to the Si QD heterojunction solar cells. The number of generated Si QDs and the photo-excited carrier lifetime was maximized when the oxygen partial pressure and boron doping concentration parameters were 2.7x10 -5 Torr and 2.27 x 10 21 atoms/cm 3 , respectively. As a result, over than 17% power conversion efficiency of Si QD heterojunction solar cell was achieved using the single layer method.Supplementary material for this article is available

Improvement of power conversion efficiency by a stepwise band-gap structure for silicon quantum dot solar cells

“…In general, the band-gap of the Si-quantum dots depends on their size due to the quantum confinement effect [27]. Up to now, the best efficiency achieved by a Si-QD solar cell with a uniform band-gap QD layer has been 17.05% [22]. However, the absorption property of the active Si-QD layer could be improved by adding a surface Si-QD layer with a higher band-gap.…”

“…In order to solve the difficulties of multilayer fabrication, a heterojunction solar cell with a single layer composed of nano sized Si-QDs was fabricated and the power conversion efficiency was improved to 14.8% [21]. Heterojunction Si-QD solar cells with a single layer improved its efficiency to 17.04% through optimization of the doping concentration and maximization of the Si-QD density [22]. However, until now, the band-gap has been fixed in the Si-QD layer, and there has been no adequate study to develop the Si-QD SC by controlling the band-gap in the light absorption layer to increase open circuit voltage (V oc ) and short circuit current (J sc ).…”

Multiple exciton generation in isolated and interacting silicon nanocrystals

“…In this context, the use of nanocrystalline solar cell devices based on tandem-like architectures may enable CM to contribute to the photocurrent more efficiently. It is important to note that, nowadays, nanostructured solar cell devices have reached high performances (more than 16% in a Si nanostructured solar cell device 215 ), an important improvement since their introduction in 2010 (initially these systems showed PCE around 3%), but there is still great space for improvement. However, in these systems, NCs are engineered to absorb high-energy photons and thus cannot be exploited to give rise to efficient CM mechanisms.…”