What is the reverse polarity lamp? Why is it brighter than conventional lamps and the price is relatively high? Today, I will take you to know what is the reverse polarity LED lamp and why it is bright.
The difference lies in the light-emitting chip inside the LED tube
. We still start from the LED light-emitting principle.
As shown in the figure above, the core component of LED light is a chip (also known as a chip). The reason why the wafer emits light is that when the positive charge at the p-type material end of the wafer is combined with the negative charge at the n-type material end, it will release energy in the form of photon radiation.
Therefore, the main components of LED chip
must include p-type material layer, n-type material layer, p-type grounding electrode, n-type grounding electrode, light-emitting layer and substrate (base).
According to the position characteristics of p-type and n-type grounding electrodes on the wafer, the wafer structure can generally be divided into: planar structure, vertical structure and flip chip structure:
(flip structure is not analyzed here)
The light-emitting chip of the reverse polarity lamp belongs to the vertical structure. Obviously, if the vertical structure has reverse polarity, it has positive polarity. The structure of the positive and reverse polarity chip is as follows:
It can be seen from the above figure that the biggest difference between the two wafers is that the positions of the n-type end and the p-type end are opposite.
Among them, the production process of p/n structure wafer is mature and the production efficiency is high. Compared with the n/p type wafer, the wafer with this structure has a layer of transparent conductive film above it. This is because the conductivity of the p-type material layer is lower than that of the n-type material layer. It is necessary to deposit a conductive film to diffuse electrons and improve the luminous efficiency.
Although it is a transparent material, the existence of a transparent conductive film will still cause a certain loss of brightness. This problem does not exist in n/p reverse polarity wafers.
N/p reverse polarity wafer is based on the preparation of p/n wafer, which reverses the wafer, peels off the original substrate layer using complex process, and then combines the p-type material layer (originally n-type material layer) to a new substrate with better conductivity and thermal conductivity (the so-called substrate transfer technology).
In this way, the n-type material layer is placed above. Due to the high conductivity of the n-type material layer, there is no need to deposit a transparent conductive film, and the light output efficiency will naturally be higher than that of the p/n-type structure wafer.
Moreover, due to the large thickness of the n-type material layer, it can also be roughened (graphically) on its surface to further increase the light output efficiency.
This is the difference between the reverse polarity lamp and the conventional lamp. The polarity of the internal chip is different, and the preparation process is complex and difficult. In actual production, the material composition is often more expensive than the chip of the conventional lamp. Of course, the price is higher.
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