Building-integrated photovoltaic (BIPV) systems represent an interesting, alternative approach for increasing the available area for electricity production and potentially for further reducing the cost of solar electricity. In BIPV systems, the visual impression of a solar module becomes important, including its color. However, the range of solar cell colours and shapes currently on offer to architects and BIPV system designers is still very limited, and this is a barrier to the widespread use of PV modules as a constructional “material.” The color of a solar module is determined by the color of the cells in the module, which is given by the antireflection coating (ARC). However, access to efficient, but differently colored, solar cells is important for the further development of BIPV systems. In this paper, we have used Diamond-like nanocomposite layer as an Antireflective Nanocomposite based (ARNAB) coating material for crystalline silicon solar cell, and the impact of varying the color of an ARC upon the optical characteristics and efficiency of a solar cell is investigated. In addition to a comparison of the optical characteristics of such solar cells, the effect of using colored ARCs on solar cell efficiency is quantified using the solar cell modeling tool PC1D.
Building-integrated photovoltaic system is the combination of aesthetic aspects, carbon-free power generation, and weather protection that makes glass-glass solar modules so attractive on building facades and roofs. Solar facades are an environmental-friendly alternative to granite, marble and other construction materials and create inspirational, functional solutions. It is with good reason that increasing numbers of builders, architects, engineers, and planners advocate this technology.
Moreover, BIPV system represents an interesting, alternative approach for electricity production and potentially for further reduction of the cost of solar electricity [
An initial investigation of the colour and efficiency of Laser Grooved Buried Contact (LGBC) solar cells as a function of the thickness of the LPCVD (Low Pressure Chemical Vapour Deposition) silicon nitride antireflection coating was reported by Mason et al. [
The deposition of silicon nitride single layer antireflection coating using plasma enhanced chemical vapor deposition (PECVD) with a dark blue color is the most commonly used process nowadays in the photovoltaic industry. However, access to efficient, but differently colored, solar cells is important for the further development of BIPV system.
In this paper, we have used Diamond-like nanocomposite layer [
Diamond-like nanocomposite films optimized for an Antireflective Nanocomposite Based (ARNAB) coating were synthesized and characterized in this work. Plasma enhanced chemical vapor deposition (PECVD) is used for DLN film synthesis [
Prior to the deposition of the films of ARNAB layer, the thickness and deposition rate of the separate films were assessed by precursor flow rate, chamber working pressure and other deposition parameters respectively. The refractive index and thickness of the deposited ARNAB layers for BIPV system were estimated by ellipsometer. In addition to experimental films optical characterization, the impact of the resulting reflection variations upon the solar cell efficiency was determined by device modeling using PC1D software.
The modeling was made by using PC1D simulation software. During modeling, textured p-type crystalline silicon had taken. Above the emitter surface, AR coating layer was considered. Simulation study was carried out by varying different coating thickness and refractive index and compared the data with experimentally observed data.
Standard n-p-p+ structured solar cell had taken with surface area 100 cm2. The Solar cell parameters used during PC1D simulations are described in Table
Solar cell parameters used during PCID simulation.
Parameter | Value |
---|---|
Bulk silicon material thickness | 200 |
Bulk doping concentration | 1016 cc |
Emitter n+ junction depth | 0.3 |
Diffusion: sheet resistance/peak doping |
45 |
Rear p+ concentration | 1 × 1019 cc |
Bulk carrier lifetime | 1000 |
Surface recombination velocity at emitter and rear surface | 10000 cm/s |
During simulation, each simulated solar cell reflectance curve was fitting with experimental reflectance curve. After matching the simulated reflectance spectra in each case, the expected solar cell parameters and illuminated current—voltage, IQE, and EQE characteristics—were, respectively, drawn as shown in Figures
Simulated solar cell’s parameters after curve fitting with experimental reflectance curve, refractive index, and thickness of ARNAB coating.
Sample | ARC thickness (nm) | ARC |
Broad band reflectance (%) | Isc (A) | Voc (V) |
|
---|---|---|---|---|---|---|
#120001B (without ARC) | — | — | — | 2.53 | 0.64 | 13.5 |
#121006 fed blue | 125 | 1.85 | 7 | 3.10 | 0.66 | 17.02 |
#121008A yellow | 175 | 1.85 | 1 | 2.99 | 0.65 | 16.03 |
#121010 magenta | 205 | 1.83 | 2 | 2.92 | 0.65 | 16.09 |
#120703B blue | 94 | 1.85 | 5 | 3.40 | 0.65 | 18.82 |
#121006B green blue | 250 | 1.85 | 1.5 | 3.00 | 0.65 | 16.51 |
#120706B dark blue | 100 | 1.85 | 1.2 | 3.49 | 0.65 | 19.35 |
ARC: antireflective coating;
*r.i: refractive index;
(a) Experimental and simulated spectral reflectance along with simulated IQE and EQE of mc-Si solar cell with fed blue colour ARC. (b) Simulated illuminated
(a) Experimental and simulated spectral reflectance along with simulated IQE and EQE of mc-Si solar cell with Yellow colour ARC. (b) Simulated illuminated
(a) Experimental and simulated spectral reflectance along with simulated IQE and EQE of mc-Si solar cell with Magenta colour ARC. (b) Simulated illuminated
(a) Experimental and simulated spectral reflectance along with simulated IQE and EQE of mc-Si solar cell with Blue colour ARC. (b) simulated illuminated
(a) Experimental and simulated spectral reflectance along with simulated IQE and EQE of mc-Si solar cell with Greenish blue colour ARC. (b) simulated illuminated
(a) Experimental and simulated spectral reflectance along with simulated IQE and EQE of mc-Si solar cell with Dark blue colour ARC. (b) Simulated Illuminated
It was observed from Table
Photographs of colour mc-Si samples fabricated by ARNAB layer deposition using PACVD technique.
In order to investigate the potential of ARNAB layer deposition techniques for fabrication of coloured antireflection coatings, a selection of target colours were made. Optimization with respect to thickness and possible adjustments in target reflectance spectra during simulation may give further improvements in efficiency.
We had shown that ARNAB coating on crystalline silicon solar cells can be tailored to give prominent colours while retaining high efficiencies. Five different colours (i.e., fed blue, yellow, Magenta, blue, greenish blue and deep blue) mc-Si wafers were fabricated by using different thickness ARNAB coating. The simulated efficiency of mc-Si solar cells was in the range from 19.35% for standard dark blue ARC to 16.03% for a yellow ARC. Fed blue, magenda, blue, and greenish blue cells all had efficiencies over 16%. This approach represents a very simple AR coating process flow for multicrystalline silicon solar cells and can be viable, short-term route to the production of differently coloured solar cells/modules for use in BIPV systems, and other applications where esthetic concerns are of importance.
This paper is dedicated to the memory of ARNAB, the one and only son of U. Gangopadhyay and Lekha Gangopadhyay. The authors would like to thank Meghnad Saha Institute of Technology, TIG for providing the infrastructural support to carry out research activity in this area. The authors also gratefully acknowledge the DST, Government of India, for financial support for carrying out solar cell related research activity.