Precision and mirror micro-grinding of micro-lens array on macro-freeform glass substrate for micro-photovoltaic performances

A hybrid of micro-lens array and freeform surface produces a novel micro-optic and micro-photovoltaic behaviors, but it is difficult to control both micro-form and macro-form accuracies in micro-machining of brittle photovoltaic glass. Hence, a ductile micro-grinding is proposed to replicate the precision-trued diamond wheel V-tip on macro-freeform glass substrate of solar cell. The objective is to understand the formation mechanism of accurate micro-lens array on freeform glass surface for photovoltaic application. First, the micro-optic properties of freeform micro-lens array were analyzed with regard to micro- and macro-shapes. Second, the precision and mirror micro-grinding along with the form errors of freeform micro-lens array was observed on the base of the transfer from brittle-mode removal to ductile-mode removal. Finally, the photovoltaic properties were experimentally measured. It is shown that the freeform micro-lens array increases luminous flux by 53.8–54.5 % compared with the plane and micro-lens array. The micro-form accuracy and the micro-structure mirror are dominated by micro-meter-scale diamond wheel V-tip with accurate wheel V-tip profile and integrated micro-grains protrusion, respectively. The novel measuring model of freeform micro-lens array may be used to evaluate and control the curved micro-form accuracy. The freeform micro-lens array contributes to the improvement of photovoltaic performance in scattered light illumination.