A boon to perovskite solar cells
Solar energy is considered to be the prime renewable energy resource that is going to govern the world in the near future due to its abundant availability and renewability. Harvesting the solar radiation into the photonic device and making the cell or panel into an effective one is a real-time problem as most of the radiation is scattered due to the physical properties exhibited by the electromagnetic radiation.
Different generations of solar cells
Many solar cells such as dye-sensitized solar cells, polymer-based solar cells, nano-dispersed solar cells, organic solar cells, and inorganic solar cells are being fabricated and available commercially. As of now, none of the solar cells have replaced the applicational utility of the first-generation silicon-based inorganic solar cell as this is the only cell that harvests the light collecting efficiency to the maximum of 25%. Second-generation solar cells include thin films such as CdTe while third-generation solar cells consist of numerous thin films that are under research and are also known as emerging photovoltaics which for sure reaches the maximum absorption and efficiency.
Perovskite solar cells (PSC) are the most considered solar cells in their third generation. Charge carriers and morphology are considered to be vital parameters in finalizing the PSC into a commercial one. Within a short span of research undertaken the efficiency of PSC has attained a quantum leap from 3.8% to 22%. Even though the attainment is near to commercial efficiency it is not readily available in the market as many factors such as environmental conditioning should be optimized before branding.
Influential parameters: Intrinsic, humidity and temperature
Environmental conditioning such as temperature difference and humidity variation that occurs in summer and winter directly affects the current density, especially the short circuit current density. This influences the efficiency of a solar cell as well as the organic material’s thermal degradation. So, these influential parameters need to be considered and optimized before fabricating the PSC.
Why has PSC not succeeded?
Even though the efficiency of PSC can compete with silicon-based solar cells, it has not commercially succeeded so far as they use lead as one of the prime ingredients in the fabrication which is much known for its neurotoxic and nephrotoxic behavior. Replacement of the lead with non-lead material enhances the compound stability but on the other hand, the efficiency gradually decreases and a much lower efficiency is being recorded.
A greater achievement is noticed from 2009 in PSC as they used organic-inorganic metal halide material viz., MAPbI3. The power conversion also drastically increased from 14% to 24% which remains still a record in the history of photovoltaic technology. Efficiency, stability, and cost are the three primary factors to be considered for the fabrication of solar cell and hence these factors are cumulatively known as the golden triangle that gauge the technical feasibility for commercialization of photovoltaic technologies. Optimization of these three independent parameters is required to draw maximum efficiency from the solar cell.
Factors to overcome the issues
In recent days, 90% of the total market has been filled with silicon-based solar cells as it is well known that their efficiency and lifetime are 21% and 25 years respectively. Even though the efficiency of PCS has reached 23%, and the cost is nearly halved, the lifetime of the cell is only about one year which is too feeble when compared with that of inorganic solar cells. So light time stabilization should be majorly considered for efficacy. When fabricating a solar module, environmental degradation such as thermal and humidity can be prevented by putting an encapsulate or barrier layer. The chemical ingredient’s spontaneous degradation over photonic exposure also should be taken into account for a maximum lifetime that limits the ion migration to a greater extent.
Thermal barriers are developed by scientists at the International Advanced Research Centre for Power Metallurgy and New Materials, Hyderabad. They have made Methyl ammonium lead diffused guanidinium iodide and moisture stability through surface passivation using 5- an amino valeric acid iodide barrier for the attainment of thermal stability. The lead content is only limited to a feeble quantity which does not produce much hazardous effect. This encapsulant layer has made the module attain high moisture and temperature stability. These materials show excellent results even when the temperature is raised to 150 plus degrees C and the life is also extended to two months. This engineered material is used in the carbon-based PSC and shows fair results thus paving a boon to the perovskite solar cells.