The scope for emerging solar cell technologies

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Climate change is one of the gravest challenges facing humankind and our planet. There is consensus among experts that this is primarily the result of human activities over the last 200 years.

Fossil fuel-based electricity generation is one of the largest contributors to climate change, it emits staggeringly large amounts of carbon dioxide (CO2) in the atmosphere. Our dependence on fossil fuels started during the Industrial Revolution. Over the years, technology has now facilitated a gigantic increase in our electricity demand to support our lifestyle and industrial needs.

Renewable energy has emerged as a prominent solution to counter the challenge of climate change and depleting resources of fossil fuels. The number of countries committing to meet the net-zero CO2 emission goal by 2050 for the global energy sectors is increasing. Clean energy harvesting technologies, solar panels, and wind turbines are safe bets presently.

Since an early observation of the photovoltaic effect in 1839 by French physicist Becquerel and the first demonstration of the first solar panel at Bell Labs in 1954, a range of photovoltaic (PV) technologies have evolved.

The first silicon solar cells exhibited a power conversion efficiency (PCE) of around 6%, almost a quarter of current world record PCEs. The first solar cells were way expensive and had limited scope for commercialization.

Solar panel technology has advanced and rapidly matured in the last one and a half decades. A range of PV technologies, like crystalline silicon (c-Si) wafer-based, thin film-based, emerging solar cell concepts (examples, Perovskite solar cells and organic solar cells), and improved panel performance have driven significant cost reductions.

Advances in Si-based solar cell PCEs and production technologies have reduced PV electricity costs drastically from $2.1/Watt (2009) to $0.28/W (2019).

With the largest share (around 97%), crystalline polysilicon is the dominant PV technology in usage. The efficiencies of Si-based solar cells are approaching the theoretical efficiency limit of 29.3%.  Improving PCEs of solar cells and panels by using innovative materials and their processing will play a crucial role in lowering cost, eco-friendly production, and ways of PV installations in the future.

According to a recent report from the International Energy Agency (IEA), solar PV installed power capacity will become the largest by surpassing that of coal by 2027. In 2022, solar PV generation increased by 26%, reaching 1300 Terawatt-hour (TWh) and its growth surpassed wind for the first time in history. This generation growth rate is well on track as envisaged by the 2050 scenario for the net-zero emissions goal in 2023-30.

As in 2022, solar PV accounted for 4.5% of global electricity generation. India recorded an impressive growth by installing 18 GW of solar PV in 2022, which is 40% higher than in 2021. The solar power tariffs in India have seen a remarkable reduction from INR 17/kWh to less than INR 2.5/kWh.

Solar panels harvest freely available sunlight for electricity and can generate and deliver electrical energy locally. They also do not emit greenhouse gas (GHG) during their operation, although there are environmental concerns in the manufacturing processes. In the long term, the net impact on the environment is favourable.

Such characteristics make solar panels a potential green electricity generating technology committed to energy security with low CO2 emissions, and distributed PV systems deployment plays an increasingly important role.

The IEA report released in 2022 validates the importance of distributed deployment enhanced capacity in the commercial and industrial (25%) and residential (23%) segments. Alternatively, utility-scale plants shared half of the global PV capacity, the lowest since 2012.

The distributed small-scale rooftop PV deployment is favorable compared to establishing large-scale PV utility installations, which face the limitation of space and cumbersome sanctioning procedures in many countries. For future effective PV deployment, distributed and utility-scale installations of solar panels need to be developed in parallel, considering the requirements and space availability.

Given an exponentially increasing rate of PV electricity generation, solar panel installations will increase multiple times in the foreseeable future. The impact of such growth of solar panel coverage within cities on urban environment-buildings and the reciprocated effects of populated areas on the performance of solar panels are also subject to investigation.

Air pollution reduces the PCE of solar panel installations by 5-15%, and this effect is prominent in highly polluted urban environments. Solar panels mounted on the building roofs affect the energy balance of the building, influencing heating and cooling loads.

Despite a few limitations, PV installations in urban settings offer overall benefits. By an estimate, buildings in urban settings consume 30-40% of total electricity consumption, which crucially contributes to GHG emissions. A building-integrated PV (BIPV) to rooftops, windows, and facades converts buildings to zero-emitting systems.

In the fight against climate change, renewable energy in the next 30-50 years is desired. To meet this, PV technologies must increase their electricity-generating share to more than 23%. Such requirements present a mammoth challenge to the PV industry and research community.

Intensive research efforts are necessary for developing various types of PV technologies parallel to Si-based solar panels. Thin film-based PV technologies have great potential with the advantages of being flexible and lightweight. Future challenges to PV energy generation offer plenty of scope for emerging solar cell technologies to find application in niche markets of diversified new deployment for increasing solar energy uptake.

Dr Samarendra Pratap Singh is a Professor in the Department of Physics, School of Natural Sciences, Shiv Nadar University, Delhi-NCR.   

The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.

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