Comparative device performance of CZTS solar cell with alternative back contact

AbstractSolar-cell performance degradation due to physical nonuniformities becomes more significant as the thickness of polycrystalline absorbers is reduced. “Voltage” nonuniformities such as those due to band-gap fluctuations, variations in the back-contact proximity, and areas where the absorber is completely depleted can have very significant impact on cell performance. Similarly local shunts can seriously degrade the efficiency. “Current” nonuniformities such as optical defects have generally much less impact. The analysis presented is based on Cu(In,Ga)Se2 cells, but the qualitative results should be applicable to thin-absorber devices in general. For lateral nonuniformity studies, the solar cell is simulated by a two dimensional network of parallel diodes separated by resistors. The nonuniformities are approximated by small regions of reduced photovoltage, often referred to as “weak diodes”, and by isolated shunt resistors. The weak-diode approach allows investigation of device performance as a function of the weak-diode voltage deficit, the ratio of weak-to strong-diode area, and the weak diodes' spatial distribution. Increased TCO resistance can isolate weak diodes, thus limiting the voltage loss due to nonuniformities, but increasing fill-factor losses.

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Mathematical modelling of a novel heterojunction SIS front surface and interdigitated back-contact solar cell

Journal of Computational Electronics ◽

10.1007/s10825-021-01735-2 ◽

2021 ◽

Author(s):

Kaustuv Dasgupta ◽

Anup Mondal ◽

Soma Ray ◽

Utpal Gangopadhyay

Keyword(s):

Solar Cell ◽

Mathematical Modelling ◽

Front Surface ◽

Back Contact

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Enhanced Charge Extraction in Metal–Perovskite–Metal Back-Contact Solar Cell Structure Through Electrostatic Doping: A Numerical Study

IEEE Transactions on Electron Devices ◽

10.1109/ted.2021.3057029 ◽

2021 ◽

Vol 68 (4) ◽

pp. 1757-1763

Author(s):

Rahul Pandey ◽

Jaya Madan ◽

Rajnish Sharma

Keyword(s):

Solar Cell ◽

Numerical Study ◽

Cell Structure ◽

Back Contact ◽

Solar Cell Structure ◽

Electrostatic Doping ◽

Charge Extraction ◽

Metal Back

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17.8%-efficient Amorphous Silicon Heterojunction Solar Cells on p-type Silicon Wafers

MRS Proceedings ◽

10.1557/proc-0910-a26-05 ◽

2006 ◽

Vol 910 ◽

Cited By ~ 2

Author(s):

Qi Wang ◽

Matt P. Page ◽

Eugene Iwancizko ◽

Yueqin Xu ◽

Yanfa Yan ◽

...

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Amorphous Silicon ◽

High Efficiency ◽

Short Circuit ◽

Open Circuit ◽

Layer Growth ◽

Surface Recombination Velocity ◽

Back Contact ◽

P Type

AbstractWe have achieved an independently-confirmed 17.8% conversion efficiency in a 1-cm2, p-type, float-zone silicon (FZ-Si) based heterojunction solar cell. Both the front emitter and back contact are hydrogenated amorphous silicon (a-Si:H) deposited by hot-wire chemical vapor deposition (HWCVD). This is the highest reported efficiency for a HWCVD silicon heterojunction (SHJ) solar cell. Two main improvements lead to our most recent increases in efficiency: 1) the use of textured Si wafers, and 2) the application of a-Si:H heterojunctions on both sides of the cell. Despite the use of textured c-Si to increase the short-circuit current, we were able to maintain the same 0.65 V open-circuit voltage as on flat c-Si. This is achieved by coating a-Si:H conformally on the c-Si surfaces, including covering the tips of the anisotropically-etched pyramids. A brief atomic H treatment before emitter deposition is not necessary on the textured wafers, though it was helpful in the flat wafers. It is essential to high efficiency SHJ solar cells that the emitter grows abruptly as amorphous silicon, instead of as microcrystalline or epitaxial Si. The contact on each side of the cell comprises a thin (< 5 nm) low substrate temperature (~100°C) intrinsic a-Si:H layer, followed by a doped layer. Our intrinsic layers are deposited at 0.3-1.2 nm/s. The doped emitter and back-contact layers were deposited at a higher temperature (>200°C) and grown from PH3/SiH4/H2 and B2H6/SiH4/H2 doping gas mixtures, respectively. This combination of low (intrinsic) and high (doped layer) growth temperatures was optimized by lifetime and surface recombination velocity measurements. Our rapid efficiency advance suggests that HWCVD may have advantages over plasma-enhanced (PE) CVD in fabrication of high-efficiency heterojunction c-Si cells; there is no need for process optimization to avoid plasma damage to the delicate, high-quality, Si wafers.

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