NOVELTY - The elongated photovoltaic device useful in monolithically integrated solar devices, comprises a sealed, cylindrical outer transparent casing (310) defining an inner volume, a substrate (102) disposed within the inner volume, a solar cell disposed on the substrate, a filler layer that occupies a space between the substrate and the transparent casing for sealing the solar cell, where the filler layer comprises a filler composition, containers (25) within the inner volume, and a diaphragm (50) sealing the first container from the layer thus defining a container volume within the container.    USE - The elongated photovoltaic device is useful in monolithically integrated solar devices.    ADVANTAGE - The elongated photovoltaic device can withstand layers of material with substantially different thermal coefficients of expansion, and can be easily assembled even in the case where the photovoltaic device is based upon a non-planar substrate.    DETAILED DESCRIPTION - The elongated photovoltaic device useful in monolithically integrated solar devices, comprises a sealed, cylindrical outer transparent casing (310) defining an inner volume, a substrate (102) disposed within the inner volume, a solar cell disposed on the substrate, a filler layer that occupies a space between the substrate and the transparent casing for sealing the solar cell, where the filler layer comprises a filler composition, containers (25) within the inner volume, a diaphragm (50) sealing the first container from the filler layer thus defining a container volume within the container, and an antireflective coating disposed on the outer transparent casing. The containers include the first container defined by a wall and an opening, which opens to the filler layer. The container comprises a diaphragm sealing the opening from the filler layer thus defining a respective container volume within the container. The diaphragm is affixed to the opening and is configured to decrease the container volume when the filler layer thermally expands and increase the container volume when the filler layer thermally contracts. The diaphragm comprises a plug, a head and a lip, is inserted into the first container through the opening under conditions of low filler layer pressure, and expands and adopts a position in the interior of the first container under conditions of high filler layer pressure. The head comprises an expandable or resilient ring that is compressed to fit into the opening of the first container thus expanding and creating a force against the wall of the first container and sealing the opening. The lip is dimensioned so that it cannot be pressed completely through the opening and into the first container. The opening is in fluid communication with the filler layer. The diaphragm is affixed to the opening of the first container and is concave with respect to a plane of the opening. The substrate is cylindrical or planer and tubular, and has a core. The inner volume is an annular space between the cylindrical substrate and the cylindrical outer transparent casing. The core of the cylindrical substrate is hollowed to form the first container. The substrate comprises first lateral and second lateral ends, and an exterior surface. The substrate is characterized by a cross-section having a bounding shape, which is circular, elliptical, a polygon, ovoid or smooth curved surfaces or arcuate edges. The outer transparent casing is tubular and encapsulates the substrate. The container volume is decreased up to 30 percent during an operating state of the photovoltaic device relative to a non-operating state of the photovoltaic device. The filler composition has a volumetric thermal coefficient of expansion of greater than 250x 10-6/ degrees C. The solar cell comprises a conducting material (104) disposed on the substrate, a semiconductor junction disposed on the conducting material, and a transparent conducting layer disposed on the semiconductor junction. The semiconductor junction comprises a homojunction, a heterojunction, a heteroface junction, a buried homojunction, a p-intrinsic-n junction or a tandem junction. The semiconductor junction comprises an absorber layer (106) and a junction partner layer. The substrate comprises plastic or glass, metal or metal alloy. The diaphragm comprises concave extension that fits into the first container. The head of the diaphragm comprises an expandable or resilient ring, which is compressed to fit into the opening of the first container thus expanding and creating a force against the at least one wall of the first container and sealing the opening. The diaphragm is a made of plastic, rubber, a rubber derivative, silicone rubber, or an elastomer. The solar cells are monolithically integrated onto the substrate, where a first solar cell is electrically connected in series to a second solar cell or a first solar cell is electrically connected in parallel to a second solar cell. The substrate or the transparent casing is rigid and made of a linear material and has a Young's modulus of 40 GPa or greater. The first container is under less than 500 Torr of pressure, and contains an inert gas.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional illustration of the layers found in a nonplanar photovoltaic device.    Container (25)    Diaphragm (50)    Substrate (102)    Conducting material (104)    Absorber layer (106)    Transparent casing. (310)