WEBVTT 1 00:00:00.080 --> 00:00:01.560 In 1965, 2 00:00:01.560 --> 00:00:03.400 an engineer predicted that we'd be able to 3 00:00:03.400 --> 00:00:05.440 double the processing power of computers 4 00:00:05.440 --> 00:00:07.320 EVERY TWO YEARS. 5 00:00:07.320 --> 00:00:08.520 And he was right. 6 00:00:08.520 --> 00:00:09.040 Since then, 7 00:00:09.040 --> 00:00:10.280 we've been pretty much been following 8 00:00:10.280 --> 00:00:12.040 this trend called Moore's law. 9 00:00:12.040 --> 00:00:14.480 Computing power has grown exponentially, 10 00:00:14.480 --> 00:00:16.880 forming the backbone of much of modern life. 11 00:00:16.880 --> 00:00:18.640 But Moore's law is breaking down - 12 00:00:18.640 --> 00:00:19.880 To make computers better, 13 00:00:19.880 --> 00:00:20.680 we've been filling them 14 00:00:20.680 --> 00:00:22.400 with more and more transistors, 15 00:00:22.400 --> 00:00:24.040 which are what create the ones and zeros 16 00:00:24.040 --> 00:00:25.400 that make computers work. 17 00:00:25.400 --> 00:00:28.440 Transistors have now shrunk to the size of one atom. 18 00:00:28.440 --> 00:00:29.960 Beyond that, there's nowhere to go, 19 00:00:30.520 --> 00:00:32.720 because the laws of physics get weird. 20 00:00:32.720 --> 00:00:34.240 A completely different sector 21 00:00:34.240 --> 00:00:36.680 where we're also hitting a wall is solar power. 22 00:00:36.680 --> 00:00:37.680 Current panels are can only 23 00:00:37.680 --> 00:00:40.560 turn around a QUARTER of sunlight into energy, 24 00:00:40.560 --> 00:00:42.560 and we can't make them more efficient. 25 00:00:42.560 --> 00:00:44.520 The reason for both is silicon, 26 00:00:44.520 --> 00:00:47.320 possibly the most important element of our time. 27 00:00:47.320 --> 00:00:49.440 It's the basis for nearly all electronics, 28 00:00:49.440 --> 00:00:51.960 and the reason we have widespread solar power. 29 00:00:51.960 --> 00:00:54.400 It's also where the famous high-tech California area 30 00:00:54.400 --> 00:00:55.560 got its name. 31 00:00:55.560 --> 00:00:57.800 But even though silicon has brought us this far, 32 00:00:57.800 --> 00:00:59.680 it can't take us any further. 33 00:00:59.680 --> 00:01:02.800 These things aren't getting more efficient. 34 00:01:02.800 --> 00:01:05.240 So, why are we outgrowing silicon, 35 00:01:05.240 --> 00:01:06.560 and what's next? 36 00:01:11.800 --> 00:01:13.200 This is pure silicon, 37 00:01:13.200 --> 00:01:14.560 but most of it naturally occurs 38 00:01:14.560 --> 00:01:17.120 as silicon dioxide, or silica. 39 00:01:17.120 --> 00:01:21.040 One of the places you'll find it is in regular old sand. 40 00:01:21.040 --> 00:01:22.920 For solar panels and electronics, 41 00:01:22.920 --> 00:01:26.360 silica is heated and refined to over 99% purity. 42 00:01:26.360 --> 00:01:27.520 Because that pure silicon 43 00:01:27.520 --> 00:01:29.600 has a particular electrical property: 44 00:01:29.600 --> 00:01:31.440 "It's a semiconductor. 45 00:01:31.440 --> 00:01:34.760 So in contrast with a conductor like copper 46 00:01:34.760 --> 00:01:37.560 that can conduct electricity easily or 47 00:01:37.560 --> 00:01:39.000 an insulator like wood, 48 00:01:39.000 --> 00:01:41.200 which won't conduct electricity at all." 49 00:01:41.200 --> 00:01:43.840 Kylie Catchpole researches solar cell technology 50 00:01:43.840 --> 00:01:46.520 and integrating solar power into the grid. 51 00:01:46.520 --> 00:01:48.240 "You need a semiconductor 52 00:01:48.240 --> 00:01:51.080 where you can control how it conducts electricity." 53 00:01:52.280 --> 00:01:53.440 In very simple terms, 54 00:01:53.440 --> 00:01:56.080 a semiconductor is like a switch. 55 00:01:56.160 --> 00:01:59.360 We can kind of turn the energy flow on and off. 56 00:01:59.360 --> 00:02:01.720 Even though silicon isn't the best semiconductor, 57 00:02:01.720 --> 00:02:02.680 it's quite a good one, 58 00:02:02.680 --> 00:02:05.160 and since there's a ton of it, it's cheap. 59 00:02:05.160 --> 00:02:06.000 For all these reasons, 60 00:02:06.000 --> 00:02:07.840 we've been using it for these two technologies 61 00:02:07.840 --> 00:02:09.320 for decades. 62 00:02:11.000 --> 00:02:13.440 1884 saw the first solar panel installed 63 00:02:13.440 --> 00:02:15.720 on a New York City rooftop. 64 00:02:15.720 --> 00:02:18.760 And in the 1950s we started making them from silicon. 65 00:02:19.520 --> 00:02:21.240 Back then, the panels converted around 66 00:02:21.240 --> 00:02:22.440 six percentage of the sunlight 67 00:02:22.440 --> 00:02:24.680 into energy and were expensive. 68 00:02:25.240 --> 00:02:28.480 Since then, efficiency has gone up to around 25%, 69 00:02:28.480 --> 00:02:29.760 and prices have come way down. 70 00:02:30.760 --> 00:02:32.360 Solar is now one of the cheapest 71 00:02:32.360 --> 00:02:34.680 forms of energy there is. 72 00:02:34.680 --> 00:02:36.080 Solar panels are made of silicon 73 00:02:36.080 --> 00:02:37.280 treated with other elements 74 00:02:37.280 --> 00:02:39.480 to form differently charged layers. 75 00:02:39.480 --> 00:02:42.100 These layers allow current to flow in one direction. 76 00:02:42.100 --> 00:02:44.400 "So if we have the electron moving, 77 00:02:44.400 --> 00:02:46.560 the electron moving is a is an electrical current. 78 00:02:46.560 --> 00:02:49.520 And so therefore it can go out and 79 00:02:49.520 --> 00:02:53.000 it can complete a circuit and it can power things." 80 00:02:53.400 --> 00:02:54.640 Just like in solar panels, 81 00:02:54.640 --> 00:02:58.480 the silicon in computers also has those layers. 82 00:02:58.480 --> 00:02:59.200 One other place 83 00:02:59.200 --> 00:03:02.080 you find these silicon layers inside a computer 84 00:03:02.080 --> 00:03:04.400 is a type of microchip called the CPU, 85 00:03:04.400 --> 00:03:06.320 or central processing unit. 86 00:03:06.320 --> 00:03:07.920 I'm going to see if I can find it in this one. 87 00:03:09.960 --> 00:03:12.200 The CPU is made up of a piece of silicon 88 00:03:12.200 --> 00:03:15.160 covered in tiny silicon transistors. 89 00:03:16.520 --> 00:03:17.640 Because of those layers, 90 00:03:17.640 --> 00:03:21.160 transistors either allow current to flow or stop it. 91 00:03:24.280 --> 00:03:28.640 Flowing current creates a 1, and no current creates a 0. 92 00:03:28.640 --> 00:03:32.480 Those 1s and 0s form the basis for all computing. 93 00:03:32.480 --> 00:03:35.040 But the silicon isn't only in the CPU - 94 00:03:35.040 --> 00:03:37.760 it's all over the inside of this computer. 95 00:03:37.760 --> 00:03:40.560 Basically, anything that needs to do any calculations, 96 00:03:40.560 --> 00:03:42.640 whether for processing or storage, 97 00:03:42.640 --> 00:03:44.400 is going to be using silicon. 98 00:03:44.400 --> 00:03:48.880 Now, tiny microchips have billions of transistors on them. 99 00:03:48.880 --> 00:03:51.480 We've had to start stacking them on top of each other, 100 00:03:51.480 --> 00:03:53.920 instead of putting them side by side. 101 00:03:53.920 --> 00:03:57.440 More transistors mean switching from 1 to 0 faster, 102 00:03:57.440 --> 00:03:59.720 which has made computing better and better. 103 00:03:59.720 --> 00:04:03.160 But we can't make silicon transistors any smaller. 104 00:04:03.160 --> 00:04:05.080 "People have reached a limitation now 105 00:04:05.080 --> 00:04:08.720 that they went to a limitation of one atomic size." 106 00:04:08.720 --> 00:04:10.720 Saravanan Yuvaraja researches 107 00:04:10.720 --> 00:04:13.080 the production of wide bandgap semiconductors 108 00:04:13.080 --> 00:04:15.400 and their use in integrated circuits. 109 00:04:15.880 --> 00:04:19.240 "And as per the physics law we cannot go below this. 110 00:04:19.240 --> 00:04:20.840 So if we cannot go below this 111 00:04:20.840 --> 00:04:22.800 then how can you make it more efficient, 112 00:04:22.800 --> 00:04:24.840 and how can you make it smaller." 113 00:04:24.840 --> 00:04:26.200 Instead of getting smaller, 114 00:04:26.200 --> 00:04:28.200 transistors need to switch faster, 115 00:04:28.200 --> 00:04:29.720 and operate at higher voltages 116 00:04:29.720 --> 00:04:31.200 to be more efficient. 117 00:04:31.200 --> 00:04:33.960 That's something silicon doesn't do very well. 118 00:04:33.960 --> 00:04:36.880 Silicon's limitations are also seriously holding back 119 00:04:36.880 --> 00:04:39.960 how much energy we can harvest from solar power. 120 00:04:39.960 --> 00:04:41.240 To understand the problem, 121 00:04:41.240 --> 00:04:43.720 we have to go down to the subatomic level. 122 00:04:44.080 --> 00:04:45.440 We need to look at electrons 123 00:04:45.440 --> 00:04:47.920 and something called the bandgap. 124 00:04:47.920 --> 00:04:50.640 The bandgap is a theoretical concept, 125 00:04:50.640 --> 00:04:53.720 but can be thought of as two bands 126 00:04:53.720 --> 00:04:55.680 with a space in between. 127 00:04:55.680 --> 00:04:58.320 The space is how much energy is required 128 00:04:58.320 --> 00:05:00.680 to move the electron from the bottom band 129 00:05:00.680 --> 00:05:02.280 to the top band. 130 00:05:02.280 --> 00:05:06.360 For silicon, the bandgap is 1.12 electron volts. 131 00:05:06.360 --> 00:05:09.840 So it requires 1.12 electron volts of energy 132 00:05:09.840 --> 00:05:12.920 to move an electron from here up to here 133 00:05:12.920 --> 00:05:14.920 where it can actually generate electricity. 134 00:05:14.920 --> 00:05:16.280 If more energy is applied, 135 00:05:16.280 --> 00:05:18.880 the electron goes past the next band. 136 00:05:18.880 --> 00:05:21.320 Then it loses energy and comes back. 137 00:05:21.320 --> 00:05:23.000 The extra energy turns into heat 138 00:05:23.000 --> 00:05:25.120 and disperses through the material. 139 00:05:25.120 --> 00:05:26.480 The smaller the bandgap, 140 00:05:26.480 --> 00:05:29.480 the more energy is lost as heat. 141 00:05:29.480 --> 00:05:31.480 Silicon has a relatively small bandgap, 142 00:05:31.480 --> 00:05:33.720 so can be prone to overheating. 143 00:05:33.720 --> 00:05:35.680 If the electron doesn't have enough energy, 144 00:05:35.680 --> 00:05:37.120 it doesn't make it to the band, 145 00:05:37.120 --> 00:05:39.680 and no electricity is generated. 146 00:05:40.720 --> 00:05:41.720 In solar panels, 147 00:05:41.720 --> 00:05:44.320 energy hits the panel in the form of sunlight. 148 00:05:44.320 --> 00:05:46.960 But the sun gives off many different types of light, 149 00:05:46.960 --> 00:05:48.480 so not all of them can be absorbed 150 00:05:48.480 --> 00:05:50.440 efficiently by silicon. 151 00:05:50.440 --> 00:05:51.960 Blue light has too much energy, 152 00:05:51.960 --> 00:05:55.000 and infrared light has too little energy. 153 00:05:55.000 --> 00:05:56.960 "So just these two facts 154 00:05:56.960 --> 00:06:00.640 limit the efficiency of solar cells to around 30%. 155 00:06:00.640 --> 00:06:05.880 And the record efficiency for silicon is already 26%." 156 00:06:05.880 --> 00:06:09.520 This narrow bandgap also wastes energy in transistors. 157 00:06:09.520 --> 00:06:11.360 "When you have very small bandgap, 158 00:06:11.360 --> 00:06:12.760 you apply one voltage 159 00:06:12.760 --> 00:06:14.480 and allow the charges to move, 160 00:06:14.480 --> 00:06:17.080 but when electrons are moving into the material, 161 00:06:17.080 --> 00:06:19.080 they also dissipate more heat. 162 00:06:19.080 --> 00:06:22.280 So this heat cannot be handled by silicon itself." 163 00:06:22.520 --> 00:06:23.920 So do we tell tech companies 164 00:06:23.920 --> 00:06:26.200 to start repainting their signs? 165 00:06:26.200 --> 00:06:28.480 Because that efficiency problem is solvable, 166 00:06:28.480 --> 00:06:30.560 by materials with wide bandgaps. 167 00:06:30.560 --> 00:06:33.200 For electronics, those include gallium nitride, 168 00:06:33.200 --> 00:06:37.120 graphene, silicon carbide, and gallium oxides. 169 00:06:37.120 --> 00:06:39.520 They allow transistors to use more of their energy 170 00:06:39.520 --> 00:06:41.360 to perform calculations. 171 00:06:41.360 --> 00:06:42.360 They lose less heat 172 00:06:42.360 --> 00:06:43.800 and can handle over 10 times 173 00:06:43.800 --> 00:06:45.600 the voltage of silicon devices. 174 00:06:45.600 --> 00:06:47.000 They also operate at twice 175 00:06:47.000 --> 00:06:48.760 the maximum temperature of silicon: 176 00:06:48.760 --> 00:06:51.400 over 300 degrees Celsius. 177 00:06:51.400 --> 00:06:52.120 Because of this, 178 00:06:52.120 --> 00:06:54.000 wide bandgap materials are already used 179 00:06:54.000 --> 00:06:56.400 in chargers for electric vehicles. 180 00:06:56.400 --> 00:06:58.640 "EV chargers and other batteries 181 00:06:58.640 --> 00:07:00.280 cannot be manufactured with silicon. 182 00:07:00.280 --> 00:07:03.480 It cannot handle such amount of current naturally 183 00:07:03.480 --> 00:07:04.800 because of its low bandgap." 184 00:07:04.800 --> 00:07:05.280 It also means 185 00:07:05.280 --> 00:07:07.960 a computer using wide bandgap semiconductors 186 00:07:07.960 --> 00:07:09.440 wouldn't need so much cooling, 187 00:07:09.440 --> 00:07:11.640 making it smaller and more energy efficient. 188 00:07:12.000 --> 00:07:14.480 And they require less energy to manufacture. 189 00:07:14.480 --> 00:07:17.840 "Recently we are also making some transistors or devices 190 00:07:17.840 --> 00:07:20.240 at room temperature at 24 degrees Celsius. 191 00:07:20.240 --> 00:07:22.840 Silicon, the minimum temperature required 192 00:07:22.840 --> 00:07:24.480 to manufacture devices out of it 193 00:07:24.480 --> 00:07:25.360 is thousand degrees Celsius." 194 00:07:25.680 --> 00:07:27.520 The materials are more expensive, 195 00:07:27.520 --> 00:07:29.560 which means they're not as widely available. 196 00:07:29.560 --> 00:07:30.880 But advances in production 197 00:07:30.880 --> 00:07:32.720 could change that in the near future. 198 00:07:32.720 --> 00:07:33.400 For solar, 199 00:07:33.400 --> 00:07:36.080 a promising wide bandgap material is perovskite, 200 00:07:36.080 --> 00:07:38.120 which can capture more of the sun's available light 201 00:07:38.120 --> 00:07:39.520 than silicon. 202 00:07:39.960 --> 00:07:42.240 "Perovskite is a crystal structure, 203 00:07:42.240 --> 00:07:44.440 and you can put different elements 204 00:07:44.440 --> 00:07:46.360 within that crystal structure. 205 00:07:46.360 --> 00:07:48.000 Then you can tune the bandgap." 206 00:07:48.000 --> 00:07:49.880 That means that you can absorb more of the light, 207 00:07:49.880 --> 00:07:52.920 making the solar panel overall more efficient. 208 00:07:52.920 --> 00:07:53.640 We'll be looking at 209 00:07:53.640 --> 00:07:55.400 what perovskite can do for solar power 210 00:07:55.400 --> 00:07:58.280 in another Planet A video really soon. 211 00:07:58.280 --> 00:08:00.800 But efficiency isn't the only concern. 212 00:08:00.800 --> 00:08:03.520 Turning that sand into silicon requires a lot of heat, 213 00:08:03.520 --> 00:08:04.920 and since most of the world's silicon 214 00:08:04.920 --> 00:08:06.360 is produced in China, 215 00:08:06.400 --> 00:08:08.560 most of that heat comes from burning coal. 216 00:08:09.391 --> 00:08:11.255 Solar panels make up for the CO2 emissions 217 00:08:11.255 --> 00:08:13.000 from manufacturing. 218 00:08:13.000 --> 00:08:14.320 Not so with microchips, 219 00:08:14.320 --> 00:08:16.160 which also use a lot of water. 220 00:08:16.440 --> 00:08:17.160 Taiwan, 221 00:08:17.160 --> 00:08:20.240 one of the biggest chip manufacturers in the world, 222 00:08:20.240 --> 00:08:21.760 has already had to ration water 223 00:08:21.760 --> 00:08:23.720 in order to keep producing them. 224 00:08:23.720 --> 00:08:25.640 And when supply shocks like that hit, 225 00:08:25.640 --> 00:08:27.160 it affects the price. 226 00:08:27.160 --> 00:08:29.320 After supply chains were disrupted during covid, 227 00:08:29.320 --> 00:08:31.080 the price of silicon shot up. 228 00:08:31.080 --> 00:08:32.200 That was one of the main reasons 229 00:08:32.200 --> 00:08:34.680 for a chip shortage that's still continuing today. 230 00:08:34.680 --> 00:08:36.080 Without silicon microchips, 231 00:08:36.080 --> 00:08:38.400 production of electronics and cars slowed down. 232 00:08:38.400 --> 00:08:39.320 And so far, 233 00:08:39.320 --> 00:08:41.920 there hasn't really been much recycling going on. 234 00:08:41.920 --> 00:08:43.880 It's easy to see why recycling silicon 235 00:08:43.880 --> 00:08:45.320 from computers is hard 236 00:08:45.320 --> 00:08:48.280 when you look at the process of taking this one apart. 237 00:08:48.280 --> 00:08:50.080 I mean, just getting into it was super difficult, 238 00:08:50.080 --> 00:08:52.200 and I didn't even pull most of the silicon 239 00:08:52.200 --> 00:08:53.720 out of the components. 240 00:08:53.720 --> 00:08:56.000 And we're about to face a huge challenge 241 00:08:56.000 --> 00:08:57.040 with solar panels. 242 00:08:57.040 --> 00:08:58.200 Most of them only work well 243 00:08:58.200 --> 00:09:00.480 for around 25 to 30 years, 244 00:09:00.480 --> 00:09:02.280 and now we're starting to see many of them 245 00:09:02.280 --> 00:09:04.080 nearing the end of their life. 246 00:09:04.080 --> 00:09:05.720 The number of used up solar panels 247 00:09:05.720 --> 00:09:07.400 is projected to increase to around 248 00:09:07.400 --> 00:09:10.320 80 million metric tons by 2050. 249 00:09:11.080 --> 00:09:13.080 So we need both new materials 250 00:09:13.080 --> 00:09:14.080 and more sustainable 251 00:09:14.080 --> 00:09:16.440 silicon production and recycling. 252 00:09:16.440 --> 00:09:18.200 Some of that is already on the way: 253 00:09:18.200 --> 00:09:20.960 EU legislation requires 80% of each solar panel 254 00:09:20.960 --> 00:09:23.440 to be recycled at the end of its life. 255 00:09:23.640 --> 00:09:26.680 The majority of panels are glass and aluminum. 256 00:09:26.680 --> 00:09:27.560 When they're are recycled, 257 00:09:27.560 --> 00:09:30.080 they're basically shredded down to their components. 258 00:09:30.080 --> 00:09:33.480 From there, the silicon can be extracted and removed. 259 00:09:33.480 --> 00:09:35.800 Silicon recycling is still in the early stages, 260 00:09:35.800 --> 00:09:37.560 but companies are already able to recycle 261 00:09:37.560 --> 00:09:39.760 around 90% of it. 262 00:09:40.160 --> 00:09:40.760 As of now, 263 00:09:40.760 --> 00:09:43.240 the silicon mostly goes to the aluminum industry, 264 00:09:43.240 --> 00:09:45.960 which combines it with other metals to make products. 265 00:09:45.960 --> 00:09:48.920 It's possible to make recycled high purity silicon, 266 00:09:48.920 --> 00:09:51.240 but the purification process is expensive, 267 00:09:51.240 --> 00:09:52.240 energy intensive, 268 00:09:52.240 --> 00:09:54.640 and not really economical at the moment. 269 00:09:55.080 --> 00:09:57.040 But the race is on. 270 00:09:57.040 --> 00:09:59.160 The silicon that has fueled the digital age 271 00:09:59.160 --> 00:10:01.080 has taken us as far as we can go. 272 00:10:02.000 --> 00:10:04.000 We need something else if we want electronics 273 00:10:04.000 --> 00:10:05.160 to keep getting better, 274 00:10:05.160 --> 00:10:08.000 and solar panels to become more efficient. 275 00:10:08.000 --> 00:10:10.120 And although there's still a lot of work to do, 276 00:10:10.120 --> 00:10:12.280 wide bandgap materials like perovskites, 277 00:10:12.280 --> 00:10:14.400 gallium nitride, and silicon carbide 278 00:10:14.400 --> 00:10:16.680 look to be the best options. 279 00:10:17.480 --> 00:10:18.800 What should we destroy next? 280 00:10:18.800 --> 00:10:19.760 Let us know in the comments 281 00:10:19.760 --> 00:10:20.920 and don't forget to subscribe, 282 00:10:20.920 --> 00:10:23.360 we've got new videos every Friday. 283 00:10:24.640 --> 00:10:25.680 Cool.