Theoretical and Experimental Analysis of Solar Cell Open Circuit Voltage Decay. Emitter, Base Lifetime and Gap Narrowing Measurements.

AbstractOpen-Circuit Voltage Decay (OCVD) is a common technique used to characterize numerous semiconductor devices. However, to the knowledge of the authors, the technique has not previously been applied to CdTe-based solar cells. We use a simple setup consisting of a function generator, rectifying diode, and digital oscilloscope to measure the dark open circuit voltage decay as a function of time across a CdTe solar cell. We find the decay to be described by the equation v(t) = v0 + A1exp (–t/τ1) + A2exp (–t/τ2) where v is the voltage, t is time, τ1 and τ2 are characteristic decay times, and A1, A2 and v0 are constants. The two characteristic decay times are on the order of 10 μs and 500 μs. The relative contribution of the two decay times depends on the magnitude of the initial applied voltage pulse. We will describe preliminary results on the correlation between the OCVD and solar cell performance, including the effects of light-soaking on OCVD behavior.

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Numerical Simulation Analysis of Ag Crystallite Effects on Interface of Front Metal and Silicon in the PERC Solar Cell

Energies ◽

10.3390/en14030592 ◽

2021 ◽

Vol 14 (3) ◽

pp. 592

Author(s):

Myeong Sang Jeong ◽

Yonghwan Lee ◽

Ka-Hyun Kim ◽

Sungjin Choi ◽

Min Gu Kang ◽

...

Keyword(s):

Solar Cells ◽

Solar Cell ◽

High Efficiency ◽

Open Circuit Voltage ◽

Surface Recombination ◽

Open Circuit ◽

Surface Recombination Velocity ◽

Metal Interface ◽

Ag Crystallites ◽

Recombination Velocity

In the fabrication of crystalline silicon solar cells, the contact properties between the front metal electrode and silicon are one of the most important parameters for achieving high-efficiency, as it is an integral element in the formation of solar cell electrodes. This entails an increase in the surface recombination velocity and a drop in the open-circuit voltage of the solar cell; hence, controlling the recombination velocity at the metal-silicon interface becomes a critical factor in the process. In this study, the distribution of Ag crystallites formed on the silicon-metal interface, the surface recombination velocity in the silicon-metal interface and the resulting changes in the performance of the Passivated Emitter and Rear Contact (PERC) solar cells were analyzed by controlling the firing temperature. The Ag crystallite distribution gradually increased corresponding to a firing temperature increase from 850 ∘C to 950 ∘C. The surface recombination velocity at the silicon-metal interface increased from 353 to 599 cm/s and the open-circuit voltage of the PERC solar cell decreased from 659.7 to 647 mV. Technology Computer-Aided Design (TCAD) simulation was used for detailed analysis on the effect of the surface recombination velocity at the silicon-metal interface on the PERC solar cell performance. Simulations showed that the increase in the distribution of Ag crystallites and surface recombination velocity at the silicon-metal interface played an important role in the decrease of open-circuit voltage of the PERC solar cell at temperatures of 850–900 ∘C, whereas the damage caused by the emitter over fire was determined as the main cause of the voltage drop at 950 ∘C. These results are expected to serve as a steppingstone for further research on improvement in the silicon-metal interface properties of silicon-based solar cells and investigation on high-efficiency solar cells.

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