Too Many Junctions? A Case Study of Multijunction Thin‐Film Silicon Solar Cells

Abstract

different energy bandgaps, multijunction solar cells can reduce the thermalization and nonabsorption losses, meaning less spectral mismatch and a better spectral utilization. The theoretical efficiency limit of the solar cell comprising infinite number of component subcells is 68.2% without concentration and 86.8% with concentration. [3] In practice, the III-V photovoltaic technology represents a very successful demonstration of both strategies. [4,5] Within this category, the benefit of multijunction concept is apparent as the record efficiency of concentrator photovoltaic cells is 29.3% for the single-junction, and grows to 34.2%, 44.4%, and 46.0% for the monolithic two-terminal double-, triple-, and quadruple-junction cells, respectively. [6][7][8][9] Multijunction solar cells can be made with two or more external electrical contacts (terminals). The components in a monolithic two-terminal device are considered to be in series connection. Therefore, the output current of a two-terminal device is constrained by the component which supplies the least photocurrent. Despite the limitation, two-terminal multijunction cells are much more feasible to design and manufacture than the ones with more terminals, thus more practical for applications. This type of two-terminal devices is the subject of this paper. For simplicity, we refer two-terminal multijunction solar cells to as multijunction solar cells, without further specification.While the multijunction III-V solar cells mark the highest achieved power conversion efficiency of photovoltaic cells to date, the multijunction concept has been explored and developed in many other photovoltaic technologies as well. Besides the reduction of losses originating from spectral mismatch, the multijunction concept offers some additional benefits to the thin-film photovoltaics. The effective absorption is split into a few separate layers in different subcells, meaning that each layer can be made thinner for the same total absorption. Such thickness reduction improves the electrical performance when the carrier transportation in the material is a limiting factor. Moreover, the division of photocurrent implies less resistive losses over the electrical interconnections. The thin-film silicon solar cell has a long history of developing multijunction solutions to make use of these advantages. The efficiency improvement by additional subcells has been shown up to the triple-junction configuration. [10][11][12][13][14][15][16][17] In organic photovoltaics, the absorber materials have rather narrow absorption spectra.

Analytical framework for the assessment and modelling of multi-junction solar cells in the outdoors

“…While these simplifications led to useful design guidelines, they impede the accurate prediction of outdoor performances. For example, the recommended global solar spectrum distribution AM1.5G has already been found as unsuitable for performance prediction of terrestrial PV cells [20,21,22,15]. Additionally, if a cell's electrical current is only implicitly given by its characteristic current-voltage relation [23], optimisation routines in a cell's design process can quickly turn complex [24].…”

“…Yamaguchi et al reviewed the progresses and challenges for integrating silicon with other materials [58]. The authors quote perovskite materials as a promising candidate for this endeavour -like many others [15,59,60]. In fact, despite their extraordinary short history as PV material [59], rapid developments already enabled 27% efficient silicon-perovskite tandem cells [60,61], exceeding the 26.7% efficiency of the current world-record single-junction silicon solar cell [62].…”

“…For thin-films, the absorption will likely be split into multiple layers as well, which requires a demanding optical modelling approach. Finally, multi-junction cells also need a more careful evaluation to seasonal parameter changes [15], like in the temperature, daytime length, solar zenith and variations in the solar spectrum.…”

Simulation of Bifacial and Monofacial Silicon Solar Cell Short-Circuit Current Density Under Measured Spectro-Angular Solar Irradiance

“…Fig. 9 shows bifacial short-circuit current density gain calculated using (5), for various sky conditions and configurations for direct, total (diffuse), upper (diffuse), lower (diffuse). Each cell has a horizontal bar depicting the gain by that particular cell configuration and sky condition.…”

Modeling of New Architecture of Photovoltaic Generator Based on a-Si: H/c-Si Materials

“…Some defects of mismatch between cells and tunnel junction costs and fabrication, are existing in the architecture of tandem solar cells proposed in literature [4]. To solve these defects, this paper establishes a new architecture of a Photovoltaic Generator (PVG), constitutes of three PV modules in series connected (previously described in abstract).…”