Progress in emerging solution-processed thin film solar cells - Part I: Polymer solar cells

Polymer solar cell (PSC), also called organic photovoltaic solar cell (OPV), is an emerging solar cell, benefitting from recent advances in nano-structured and functional energy materials and thin films, making it a cutting edge applied science and engineering research field. The driving force behind the development of PSCs is the need for a low-cost, scalable, flexible, light-weight, and easy to manufacture power source, something that does not have the disadvantages of crystalline silicon and inorganic thin film solar cells. The fact that most layers of organic solar cells can be made from materials that can be processed in solution and deposited using low-cost casting methods in ambient conditions is a great advantage of solution-processed (SP) solar cells (SCs). The unique characteristic of this review, compared to other reviews, is its focus on solar cell materials and scalable fabrication techniques that are compatible with the concept of solution-process-ability. Following this perspective, in this paper, an overview of the principle of operation, recent progresses within the past few years, current challenges, and innovations pertinent to each layer of SP-PSCs and the entire device are provided. Detailed discussion on suitable materials for each layer, the effects of solvent treatment on nano-structure of each layer, cell stability and lifetime, and the state-of-the-art scalable methods suitable for large scale manufacturing of SP-PSCs are reviewed. At the end, future research trends in the area are deliberated. In Part II, recent advances in lead halide perovskite solar cells will be reviewed.