Cost model for LIMA device Vázquez, M.A.; Connolly, J.P.; Cubero, O. ...
Energy procedia,
2011, 2011-00-00, Volume:
8
Journal Article
Peer reviewed
Open access
In this paper we show the results of the cost model developed in LIMA project (FP7-248909). The LIMA project is titled “Improve photovoltaic efficiency by applying novel effects at the limits of ...light to matter interaction”. The project started in January 2010 and during this year a cost model of the device developed in the project has been developed to assess the industrial viability of this innovative approach to increase the efficiency and reduce the cost of photovoltaic solar cells. LIMA project exploits cutting edge photonic technologies to enhance silicon solar cell efficiencies with new concepts in nanostructured materials. It proposes nano-structured surface layers designed to increase light absorption in the solar cell while decreasing surface and interface recombination loss. Integration in a back contact design further reduces these interface losses and avoids shading. The project improves light-matter interaction by the use a surface plasmonic nanoparticle layer. This reduces reflection and efficiently couples incident radiation into the solar cell where it is trapped by internal reflection. Surface and interface recombination are minimized by using silicon quantum dot superlattices in a passivating matrix. The distance between quantum dots ensures wave-function overlap and good conductivity.
In this work, a photovoltaic mini‐module combining interdigitated back‐contacted solar cells with black silicon in the front was implemented as a proof of concept. The module consists of nine solar ...cells connected in series with an active area of 86.5 cm2. Both the assembly and panel encapsulation were made using industrial back‐contact module technology. Noticeable photovoltaic efficiencies of 18.1% and 19.9% of the whole module and the best individual cell of the module, respectively, demonstrate that fragile nanostructures can withstand standard module fabrication stages. Open‐circuit voltage and fill factor values of 5.76 V and 81.6%, respectively, reveal that series interconnection between cells works as expected, confirming a good ohmic contact between cell busbars and the conductive backsheet. Additionally, the excellent quasi‐omnidirectional antireflection properties of black silicon surfaces prevail at module level, as it is corroborated by light incidence angle dependence measurements of the short‐circuit current parameter.
A photovoltaic mini‐module combining interdigitated back‐contacted solar cells with black silicon in the front was implemented. The module consists of nine solar cells connected in series with an active area of 86.5 cm2. Both the assembly and panel encapsulation were made using convectional industrial back‐contact module technology. A noticeable photovoltaic module efficiency of 18.1% demonstrates that fragile nanostructures can withstand standard module fabrication stages.
In this paper, we propose the design and fabrication of a novel heterojunction semiconductor–insulator–semiconductor (SIS) front surface and interdigitated back-contact (IBC) solar cell. We ...approximate the performance parameters and loss analysis of the proposed solar cell using MATLAB software programming. Many studies have reported the experimental analysis of amorphous silicon (a-Si) IBC solar cells. A number of silicon heterojunction solar cell designs with promising efficiency have been reported in the past few decades. In this study, a long-lifetime (~ 2 ms)
n
-Si substrate was considered so that a sufficient number of photogenerated carriers could reach the interdigitated layer and be absorbed. The availability of carriers at the interdigitated back surface was further enhanced by considering a high-low junction created by a ZnO
n
+
layer at the front surface. A very thin layer of thermally deposited insulator SiO
2
was considered between the ZnO and
n
-Si. This layer reduces the detrimental effects of interface defects. This is the first study in which we have theoretically investigated an IBC solar cell using metal oxide semiconductor layer deposition, thereby avoiding the expensive and complicated doping and diffusion process. In general, a high-concentration
n
+
layer is doped to create a high-low junction at the front to accelerate the transport of carriers to the back junctions. We propose a cost-effective method using thermal deposition of a SiO
2
layer followed by sol–gel ZnO layer deposition, which serves the same purpose as an
n
+
layer by introducing an SIS junction potential at the front. The interdigitated back surface was designed with sequential
n
+
a-Si and
p
+
a-Si vertical junctions.
Annealing effects have been studied on test structures and TLM pads to determine the optimum final annealing time for fabricated interdigitated back contact (IBC) solar cells. Initial results show ...that passivation will recover after 3 min annealing at 200 °C but will degrade by further annealing. Contact resistance measurement performed on TLM structures both for emitter and base stack show that by increasing the annealing time the contact resistance will increase. Using the initial annealing time of 5 min, we obtain a short circuit current density of 37 mA/cm 2 and open-circuit voltage of 691 mV, leading to a conversion efficiency of 19.3%.
Back-contact back-junction solar cell has the potential for high efficiency energy conversion due to the distinctive architecture of the device. The fabrication processing for these types of cells ...requires high material quality and complicated processing technology involving many masking and alignments steps which results in the increase of the manufacturing costs. Within the LIMA EU Project, we developed a novel process architecture for Interdigited-Back-Contact (IBC) front surface field (FSF) solar cells obtained by optimization of the fabrication process using only industrially feasible technology (i.e. screen-printing, laser ablation and conventional diffusion processes). With this process we have obtained cell efficiencies above 19% on n-type silicon 2x2cm2 float zone (FZ) substrate. Moreover, we have integrated this process with innovative methodology which opens new possible solution to the already well established techniques. This approach allowed us to improve the front side with excellent proprieties of passivation and conductivity and to implement interdigitated phosphorous back surface field (BSF) and boron emitter in a single mask process. The solar cells results of this improved front side are presented in comparison to the solar cells with IBC-FSF architecture.
We report on the theoretical investigation of a silicon-based interdigitated back contact back heterojunction (BHJ) solar cell that combines the advantages of heterojunction with intrinsic thin layer ...(HIT) solar cell and point contact back junction c-Si solar cell. Our results show an optimum bandgap for emitter (p-type a-Si:H) layer for this cell to be approximately 1.72eV. As we increase the bandgap from 1.3eV to 2.2eV, the open circuit voltage (Voc) increases from 0.45V to 0.75V and then saturates, while the short circuit current density (Jsc) remains constant at 35mA/cm2 up to about 2.0eV, and then decreases to zero. Fill factor (FF) increases from 57% to a maximum of 75% as the bandgap increases from 1.3eV to ∼1.72eV, respectively, and then decrease to 5% when the bandgap reaches 2.1eV. Efficiency increases from 7% and reaches a maximum of about 19% at around 1.7eV and then decreases to zero at 2.1eV. These results can be correlated to changes in valance band spike (barrier) when emitter bandgap increases from 1.3eV to 2.2eV, and are explained in terms of band alignment between p-a-Si:H/i-a-Si:H/n-type-c-Si.
► In the point contact structure undoped region at the rear side acts as reflector. ► Doped regions are shrunk to points and provide more space for undoped region. ► Point contact structure enhances reflection from the rear side. ► In the literature, no reason has been reported for choosing emitter bandgap of about 1.7eV. ► Improved band alignment enhances efficiency to a maximum when emitter band gap is around 1.7eV.
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