TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The array further comprises: an isolation diode disposed beneath the first cell, where the isolation diode comprises a p-n junction or a p-i-n junction having a polarity opposite a polarity of the first cell; a graded- composition layer disposed beneath the first cell, where the graded-composition layer relieves at least a portion of a lattice-mismatch strain between the substrate and the first cell; a constant-composition silicon germanium layer disposed between the first and second portions of the graded-composition layer, where the constant-composition layer has a germanium content equal to the intermediate germanium content; for each solar cell, a first contact to the cap layer and a second contact to a layer disposed beneath the first cell, where each of the first and second contacts are disposed over a top surface of the substrate; for each bypass diode, a first contact to a top surface of the first cell and a second contact to a layer disposed beneath the first cell, where each of the first and second contacts is disposed over the top surface of the substrate; at least one additional series string of discrete solar cells on the substrate, where the series string and the additional series string are connected in parallel; interconnection circuitry on the substrate between each of the discrete solar cells; electrically connected to the series string, circuitry for maximum power point tracking, where the circuitry comprising a direct current/direct current converter; electrically connected to the circuitry, a charge-storage element; and an insulating layer disposed in or above the substrate. The isolation diode comprises silicon germanium having a bandgap smaller than a bandgap of the first cell. A first portion of the graded-composition layer comprises silicon germanium and is disposed between the substrate and the isolation diode. A second portion of the graded-composition layer comprises silicon germanium and is disposed between the isolation diode and the first cell, where the first portion grades from an initial germanium content to an intermediate germanium content larger than the initial germanium content and the second portion grades from the intermediate germanium content to a final germanium content larger than the intermediate germanium content. At least one of the solar cells comprises a silicon cap layer disposed over the second cells. The first contact comprises a silicide of a metal and the second contact comprises a germanosilicide of the metal. The first contact comprises a germanosilicide of a metal and the second contact comprises a germanosilicide of the metal. The first contact covers all of a top surface of the first cell of the bypass diode, thus preventing its solar illumination. The interconnection circuitry between at least two of the discrete solar cells comprises a switching element enabling reconfiguration of the electrical connection between the at least two discrete solar cells. The interconnection circuitry between each of the discrete solar cells comprises a switching element enabling reconfiguration of all of the electrical connections between the discrete solar cells. The circuitry is disposed over a top surface of the substrate and the charge-storage element is disposed under a bottom surface of the substrate opposite the top surface. The second cells of at least one solar cell are substantially free of aluminum. For at least one solar cell, at least one of a boundary between the first cell and the second cells or a boundary between second cells of the second cells is free of a bonded interface. For at least one solar cell, the first cell comprises a silicon germanium p-n junction or a silicon germanium p-i-n junction.