Photovoltaics & Solar Cells

Solar photovoltaic technology converts light into electricity at the atomic level. The photoelectric effect causes certain semiconductor materials to absorb sunlight particles or photons, and release electrons. A photovoltaic cell produces electricity from visible light; a solar cell absorbs the full range of light frequencies, not just visible light, from sunlight and converts solar radiation into useful energy. As a safe, sustainable, and efficient source of energy, photovoltaic and solar cell systems are used for network or isolated power generation in many types of devices, from electric vehicles (EVs) and solar roofs to water pumping and desalination systems.

Photovoltaic cells utilize layered semiconductor materials as a PN junction to convert light energy in the form of photons to electric current in the form of electrons. The PN junction is an interface between a p-type semiconductor (electron acceptor material) and an n-type semiconductor (electron donor material). When the photon is absorbed by the n-type semiconductor, an electron is dislodged, generating a free electron and electron-hole pair. The negatively charged electron is attracted to the p-type material, and the positively charged hole is attracted to the n-type material. If a completed circuit is connected to the electrodes, the free electron will travel through the circuit, creating electric current and voltage, until it recombines with an electron-hole back in the p-type material.

The efficiency of photovoltaic systems vary by the type of photovoltaic cell technology and the type of semiconductor material used. The first solar cells were composed of inorganic polycrystalline and single-crystalline materials. Notable progress has been made in photovoltaic technology due to remarkable advancements in organic electronics and materials.

An organic solar cell is lightweight, flexible and can be produced at low cost with high-performance polymeric donors, fullerene, and non-fullerene acceptors (NFAs) through low-temperature solution processes on a transparent conductor, such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO). Organic hole-transport materials (HTMs) have enabled high-performance perovskite solar cells as an alternative, more efficient method for harvesting solar energy.

Perovskite solar cells typically use a hybrid inorganic-organic material as the light-harvesting active layer. Perovskite solar cells benefit from a high conversion efficiency, low cost, and simple manufacturing, making them the fastest advancing solar technologies for commercial applications. Lead halide perovskites have the highest conversion efficiency and are the fastest growing solar cell technology.