CLEMSON– Contrary to media hype, there are no prospects of manufacturing perovskite solar cells for large scale manufacturing.

Rajendra Singh, the Clemson University D. Houser Banks Professor of Electrical and Computer Engineering, current Ph.D. student Amir A. Asif, and former Ph.D. student Dr. Githin F. Alpatt have published a paper titled “Technical and Economic Assessment of Pervoskite Solar Cells for Large Scale Manufacturing”, in the Journal of Renewable and Sustainable Energy (7, 043120 (2015); doi: 10.1063/1.4927329). Singh is a veteran of the photovoltaic industry and a 2014 White Hose Champion of Change for solar deployment,

Free fuel based direct conversion of solar energy into electrical energy   by photovoltaics  (PV) is emerging as the lowest cost technology for generation of electrical power. In certain locations, PV generated electricity cost in the United States   has reached as low as $0.0387 per KWH. The global cumulative installed PV capacity has reached the 180 gigawatt (GW) milestone at the end of year 2014. Over 90 percent of PV market share consists of non-concentrator bulk silicon solar cells. Silicon based PV modules have taken the same role in power industry as has been the role of silicon CMOS based integrated circuits in microelectronics and nanoelectronics. Future research direction of photovoltaic devices must take into consideration the current manufacturing trends of the PV devices in the global context of electricity generation

In recent years, perovskite or organo-metal halide perovskite (OHP) solar cells have received lot of attention from media. For ultra-small area of the order of 0.1 cm2, efficiency of 20 percent or so are reported. However, for area of 25 cm2, the efficiency is about 10 percent. Progress in reported efficiency of small area perovskite solar cells and the increase in the number of publications are the key reasons for media attention. However, it should be noted that the exponential growth in publications and increase in efficiency do not necessarily translate into real world success, and it does not guarantee that the product will be manufactured. There are many such examples in the semiconductor world.

The general field of photovoltaics is 61 years old, and the terrestrial photovoltaics is 42 years old (a lot of PV research started just after oil embargo of 1973). Based on the existence of a wide variety of fundamental technical and economical knowledge base, we have  examined the potential of perovskite solar cells for large scale manufacturing.

Process variability is one fundamental obstacle in the manufacturing of perovskite solar cells. The process control used in the fabrication of solar cells results in devices with variable power output. A statistical analysis showed that an increase in standard deviation of solar cell parameters has direct impact on power output, and power loss is a function of parametric variation. To provide controlled process variability, the semiconductor industry uses advanced process control in place of statistical process control. This adds to the capital cost of manufacturing equipment and operating cost of particular process equipment. In addition to that, for a new type of solar cells, the cost of custom built processing equipment is much higher than “off the shelf” equipment used by silicon solar cell manufacturers. This issue of process control has been one of the fundamental reasons for failure of over 200 companies that started in 2008 with the goals of inventing and commercializing disruptive PV technologies; most of these companies have either gone bankrupt or do not exist anymore.

Besides the scaling up issues mentioned above, there are series resistance issues that get masked when cells of smaller size are tested and reported. If a solar cell is smaller than a certain size, the measurements will not reflect the effects of series resistance. This is due to the fact that the resistance of the solar cell is a non-linear function of current.

The stability issues will be a major roadblock for commercialization of perovskite solar cells. Pervoskite solar cells have shown degradation in 5 hours of exposure to light. The reliability data of silicon solar cells have shown that silicon solar cells can operate very well beyond the 25 years warranty given by the manufacturers. Sun Power has published that useful life of their modules is more than 40 years, which is defined as 99 percent of modules producing at least 70 percent of their power. Very recent research work has shown that the use of silicone as the embedded material in place of ethyl vinyl acetate (EVA) in module manufacturing will increase the lifetime of silicon solar cells to 50 years.

Based on the photovoltaic module manufacturing requirements of no constraint on the supply of raw materials, low variability of every key process and process-induced defects, low cost of manufacturing, prospects for further cost reduction in the future, green manufacturing, and long-term reliability, there are absolutely no prospects of manufacturing perovskite solar cells. No one has commercialized perovskite solar cells. The hype created in the literature has no technical and economic evidence to support the claim that silicon solar cells will be replaced by perovskite solar cells. The research team also concluded that there is no future of perovskite solar cells to increase the efficiency of silicon solar cells either by using two or four terminal device structure.