Concept: Researchers at Stanford University have developed a new thin and flexible solar panel with improved efficiency. The new solar panel is developed using transition metal dichalcogenides (TMDs) that absorb high levels of sunlight that strike their surface compared to other solar materials. Under standard solar radiation conditions, the new panel displayed an efficiency of 5.1% and a power per weight return of 4.4 W/g.
Nature of Disruption: TMDs are two-dimensional (2D) materials with exceptional semiconducting properties and high optical absorption coefficients, making them suitable for the manufacture of semi-transparent and flexible solar cells. The new solar cell is developed with an ultrathin, lightweight, and flexible polyimide (PI) substrate with a thickness of 5μm, transparent graphene contacts doped with molybdenum oxide (MoOx), and multi-layer tungsten diselenide (WSe2) absorbers measuring 200nm. It also includes passivation and anti-reflection coatings, and optically-reflective electron-collecting gold bottom contacts. The use of graphene contacts enables it to mitigate Fermi-level pinning, a phenomenon that occurs in solar cells when an energy barrier is created for electrons and holes by bending the bands at the semiconductor interface. The new solar cell claims to outperform organic and perovskite solar cells and also helps to overcome the stability challenges associated with organic and perovskite solar cells.
Outlook: Fermi level pinning is one of the challenges faced by normal TMD solar cells and it is responsible for limiting the power conversion efficiency of the TMD solar cells to around 2%. The Fermi levels define the efficient conversion of the energy of radiation into electrochemical energy. Leveraging graphene contacts, the new solar cell claims to overcome the challenge of Fermi level pinning. Also, the present solar cells based on silicon are heavy, bulky, and rigid for applications where flexibility, lightweight, and high power are required. Researchers claim that the new solar cells are flexible for applications in wearable devices, aerospace, and electric vehicles.