NOVELTY - Thermocleaving a thermocleavable polymer layer which is in thermal contact with a heat sensitive component that is not tolerant of the temperature required for thermocleavage of the thermocleavable polymer layer, involves: illuminating the layer with a light source having a wavelength range more strongly absorbed by the thermocleavable polymer and less strongly absorbed by the heat sensitive component, such that the thermocleavable polymer layer reaches a temperature to cause thermocleavage of the polymer without causing detrimental heating to the heat sensitive component.    USE - For thermocleaving a thermocleavable polymer layer useful for manufacturing photovoltaic device (claimed) (solar cells).    ADVANTAGE - The use of a light source of an appropriate narrow wavelength range to heat a thermocleavable polymer layer can produce the required temperatures in that layer for rapid thermocleavage of the thermocleavable substance, without a detrimental level of heating of the underlying layers or substrate i.e. heat sensitive component. The use of an LED light source has the advantages of lower cost and greater robustness compared with the use of a laser light source, and in addition, a wide selection of wavelength ranges are accessible using LEDs. The use of a laser has the advantage of providing very high intensity light, with the ability to focus the light on to a desired area of the item.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for apparatus for thermocleaving a thermocleavable polymer layer which is in thermal contact with a heat sensitive component that is not tolerant of the temperature required for thermocleavage of the thermocleavable polymer layer, where the thermocleavable polymer layer is provided on a web containing a heat sensitive component, comprising: an oven adapted to allow the passage of the web through it; a source of illumination positioned to illuminate the web during or after its passage through the oven; and a conveyor defining the path of the web for transporting the web through the oven and past the illumination source, containing a reel on which the web is wound.