Extremely high efficiency solar cells are described. Novel alternating bias schemes enhance the photovoltaic power extraction capability above the cell band-gap by enabling the extraction of hot carriers. In conventional solar cells, this alternating bias scheme has the potential of more than doubling their yielded net efficiency. In solar cells incorporating quantum wells (QWs) or quantum dots (QDs), the alternating bias scheme has the potential of extending such solar cell power extraction coverage, possibly across the entire solar spectrum, thus enabling unprecedented solar power extraction efficiency. Within such cells, a novel alternating bias scheme extends the cell energy conversion capability above the cell material band-gap while the quantum confinement structures are used to extend the cell energy conversion capability below the cell band-gap. Light confinement cavities are incorporated into the cell structure to allow the absorption of the cell internal photo emission, thus further enhancing the cell efficiency.