{"id":12111,"date":"2017-06-14T16:30:18","date_gmt":"2017-06-14T06:00:18","guid":{"rendered":"https:\/\/www.solarquotes.com.au\/blog\/?p=12111"},"modified":"2025-09-04T10:59:08","modified_gmt":"2025-09-04T01:29:08","slug":"phono-introduces-mwt-panels-dotty-idea-improving-efficiency","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/phono-introduces-mwt-panels-dotty-idea-improving-efficiency\/","title":{"rendered":"Phono Introduces MWT Panels:\u00a0 A Dotty Idea For Improving Efficiency"},"content":{"rendered":"
\"robin

Phono Solar have only gone and drilled holes in their new solar panels…<\/p><\/div>\n

If you want a solar cell to produce electricity then it’s important to let the sunshine in<\/a>.\u00a0 Specifically, into the solar cell.\u00a0 Not letting the sunshine in is a bad idea.\u00a0 Despite how very important this is, most solar cell manufacturers place a fine metal wire grid on top of their cells that blocks around 5% to 6% of sunlight falling on them, for no other reason than they don’t work without it.\u00a0 It appears the metal grid is necessary to make electrical contacts required for current to flow.<\/p>\n

One way to reduce the amount of light blocked by the electrical contacts on the surface of cells is to use Metal Wrap Through technology, or MWT for short.\u00a0 Instead of having wires run across the surface, a “laser<\/a>” is used to cut holes into cells for electrical contacts and very fine wires called “fingers” radiate across the cell from them.\u00a0 Compared to using a grid, this method halves the amount of light blocked.<\/p>\n

While MWT cells have been made since at least 2010<\/a> and panels since at least 2013, they have never really caught on.\u00a0 I’ve never seen one in Australia.\u00a0 But this may be about to change.\u00a0 Phono Solar<\/a> introduced its new MWT panel<\/a> at the Tokyo solar conference in March this year1<\/a><\/sup> and it should be arriving in Australia in the near future.<\/p>\n

Because MWT provides an efficiency advantage at a price that appears to be cost effective, more manufacturers may follow Phono’s lead and provide MWT panels in the future.\u00a0 While I don’t know if this technology has legs, I can say it definitely has “fingers”.<\/p>\n

How Solar Cells Work<\/h2>\n

When light hits a suitable piece of silicon or other semi-conductor2<\/a><\/sup> it can cause electrons to be knocked out of the atoms they were hanging around.\u00a0 This is apparently very thrilling for them, because after it occurs they are called “excited electrons”.\u00a0 By adding tiny amounts of right elements to the top and bottom sides of a silicon wafer, a junction can be formed that stops electrons that are knocked below it from going back to the atoms they came from because of magic — I mean physics.<\/p>\n

But if a metal conductor is attached to the top and bottom of a solar cell, electrons can travel along it from the top to the bottom to where they can then do it all over again if they like.\u00a0 On the way, as they are traveling through the conductive wire, they can be made to do work, such as powering an LED light, charging a laptop, or passing through a solar inverter that will change their direct current (DC<\/a>) to the alternating current (AC<\/a>) the grid uses.<\/p>\n

How MRT Solar Cells Work<\/h2>\n

The metal conductors on top of a solar cell are a problem because sunlight has a hard time passing through metal.\u00a0 If you ever come across light that easily passes through metal then what you are probably dealing with is not sunshine, but some kind of “laser<\/a>“.<\/p>\n

SunPower<\/a> solves this problem by putting a transparent conductive layer on top of the cell instead of wires.\u00a0 They do this with their X and E series panels and LG Solar appears to do the same with their NeON2 R panels<\/a>.\u00a0 Unfortunately, while it works well, this option is not cheap.\u00a0 Another solution is to use small solar cells that overlap, so the electrical contacts of one cell are covered by the cell on top.\u00a0 This method is used by several manufacturers including SunPower in their Performance Series<\/a> panels:<\/p>\n

\"SunPower

An example of overlapping solar cells in a SunPower P-Series panel.<\/p><\/div>\n

MWT doesn’t prevent all shading from electrical contacts, but it does cut it by around half or more.\u00a0 This is done by eliminating the need for the thickest wires that run across the top of a cell called busbars.\u00a0 Instead of having them on the surface, Metal Wrap Through wraps metal through the solar cell by cutting holes in it with a “laser<\/a>” and placing metal electrical contacts in them.\u00a0 From the contacts spread extremely fine metal wire “fingers”.<\/p>\n

The Phono MWT cells have 25 holes each.\u00a0 As you can see below, this makes them look rather dotty:<\/p>\n

\"MWT<\/p>\n

In case you are wondering, these are not quantum dot<\/a> solar cells.\u00a0 Quantum dots are less than half that size.<\/p>\n

Potentially Half A Percentage Point Efficiency Improvement<\/h2>\n

MWT can increase the amount of light entering a solar cell by 2.5% or more.\u00a0 For a 16% efficient panel a 2.5% increase in sunlight entering cells increases its efficiency to 16.4% and would increase an 18% efficient panel to 18.45%.<\/p>\n

MWT Improves Heat Tolerance<\/h2>\n

Lasering 25 holes through a solar cell and stuffing them with highly conductive metal is apparently very useful for transferring heat from the surface of a solar cell to the back.\u00a0 Phono says:<\/p>\n

“…the operating temperature is 3-5 degrees Celsius less than that of the traditional modules, which allows an additional 2% power generated.\u201d<\/p><\/blockquote>\n

This means if a typical solar panel has its efficiency reduced by 0.4% for each 1 degree increase in temperature about then MWT panels should only have their efficiency decline by about 0.3%3<\/a><\/sup>.<\/p>\n

MWT May Save On Materials<\/h2>\n

MWT panels are not a new idea.\u00a0 People have been working on them and producing them for years now, but so far not a great deal has come of them.\u00a0 A major reason why it can take so long for advances that work in the lab to take off in the market is because it is often difficult to work out how to mass produce them cost effectively.\u00a0 An important part of this process is often lowering the cost of materials used.<\/p>\n

Phono claims its MWT panel reduces the need for silver paste4<\/a><\/sup>.\u00a0 If this is correct, it’s an important development as one of the disadvantages of MWT cells used to be they required more silver.<\/p>\n

MWT cells also apparently suffer less breakage during panel manufacture, which is another useful way of lowering manufacturing costs.<\/p>\n

Provided both material and manufacturing costs aren’t much higher than those of standard panels, then MWT will be able to compete with other methods of improving efficiency.\u00a0 While overlapping cell panels are capable of slightly higher efficiency because it is possible to make them so they don’t block any light, they do have the added expense of requiring extra silicon because of overlapping, so it will be interesting to see which method will win on price per watt.<\/p>\n

MWT Panels Look Pretty — If Installed 3 Feet From Your Face<\/h2>\n

Phono’s MWT panel looks very pretty close up.\u00a0 Here’s a picture provided by Phono which for some reason only has 16 “laser<\/a>” holes per cell instead of the 25 their other panels do:<\/p>\n

\"MWT<\/p>\n

The fine wire “fingers” surrounding the contacts in the holes look kind of like little snowflakes or maybe coral polyps.\u00a0 Phono says the patterns can be customized to suit people’s preferences.\u00a0 Here are some examples from 2013 by Tianwei New Energy:<\/p>\n

\"Finger<\/p>\n

Don’t they look wonderful?\u00a0 Wouldn’t you love to be able to customize solar panels like this if you were some kind of nutter in the habit of installing solar panels three feet from your face?<\/p>\n

Should You Buy MWT Panels?<\/h2>\n

While MWT panels haven’t taken off so far, maybe their time has arrived and we’ll soon see multiple panels with the technology appearing on the Australian market.\u00a0 So you may be wondering whether or not you should buy MWT panels.<\/p>\n

Personally, I say you shouldn’t really care whether or not a panel is MWT.<\/p>\n

Not many people in the market for rooftop solar are experts on the technology.\u00a0 To expect the average person to decide whether it is better to put grids on solar cells, laser holes in them, overlap them, or slap a transparent conductive layer on top is basically nuts.\u00a0 Most people simply don’t have the background required to judge the benefits of different types of solar panel technology.<\/p>\n

But what anyone can do is:<\/p>\n