We design a wedge-shaped microprism sheet suited for upright solar panels to mitigate their reflection and waveguiding losses. This microprism sheet achieves a surface reflectance of below 1% for all incident angles. Moreover, it effectively funnels transmitted rays within a narrow angular range of ±15° from the normal line, thus minimizing reflection at multiple interfaces. These optical characteristics substantially enhance the photovoltaic performance of solar panels, yielding a more pronounced increment at larger incident angles, as evidenced by indoor and outdoor experiments. Notably, outdoor testing demonstrates consistent superior performance of upright solar panels covered with the microprism sheet, irrespective of the orientation of their faces. The developed microprism sheet shows promise for scalability up to meter scales and compatibility with various photovoltaic materials.