Fig. 2

a Planar and b orthogonal cells can be modeled as an array of parallel connected solar cell segments. As illustrated, planar solar cell segments experience uniform illumination throughout the device. However, in the case of orthogonal solar cells, each segment acts as an optical filter and removes a portion of the light entering in the next segment. This leads to a non-uniform illumination intensity or spectrum at each of the orthogonal solar cell segments and analogy comparable to tandem solar cells. The consequence of this non-uniformity is illustrated in c, where orthogonal solar cell under illumination and operated at its maximum power point would comprise of energy generating segments, open circuit segments, and energy consuming segments. Lower segments are exposed to lower light intensity but operate at the same voltage as the upper segments as all the segments are parallel connected. The lower light intensity at lower segments and there operation voltage result in their operation in the energy consuming mode. The lower segments draw current and consume energy generated by upper segments in order to achieve the same output voltage. This is due to the variation in the current-voltage characteristics of different segments exposed to a variable illumination as highlighted in d