Light management for reduction of bus bar and gridline shadowing in photovoltaic modules

Abstract

Solar cells used in photovoltaic (PV) crystalline silicon modules commonly feature grid fingers and bus bars as front contacts. The grid fingers and bus bars partially block the sunlight from reaching the semiconductor layers of a solar cell and therefore reduce the efficiency of a solar module. In this paper, we present experimental results of different technologies to reduce the shadowing effect that bus bars and grid fingers impose. We focus on two technologies that can be easily integrated into standard PV module technology and help to increase the module's efficiency. In the first technology, a laser is used to create a scattering pattern on the front glass of the module. This pattern directs light away from the bus bars and grid fingers. In the second technology, the bus wires are coated with a diffuse reflective coating. The sunlight is diffusely reflected at this coating. A part of it is reflected at such angles that internal reflection at the front surface of t he cover glass occurs. From there the light is reflected back to the solar cell and contributes to the generated photocurrent

Approaches to improving energy yield from PV modules

“…First, losses that result from the shadowing effect of bus bars on front contact crystalline silicon cells can be minimized by either patterning the overlying glass or by painting a diffuse reflective layer on the on the surface of the bus bar. 5 Second, a textured front-side glass can be used to increase the transmission of incident sunlight, as well as ensuring that a portion of the reflected outbound light is totally internally reflected back into the module affording a further chance at absorption in the solar cell. …”

PV Module Technology and Reliability – Status and Perspectives

“…If the interconnector surface is structured [23] or coated [16] to deflect normally incident light, even 1 -2% coupling gain can be achieved after encapsulation.…”

Colored Ribbons Achieve +0.28%$_{\bf abs.}$ Efficiency Gain

“…Unfortunately, these cell connectors only work well for perpendicularly incoming radiation [10]. Jaus et al [12] use a scattering front glass and a diffuse reflector on the grid to decrease the optical losses of the front grid.…”

“…Colored ribbons scatter incoming photons and, due to subsequent total internal reflection at the glass/air interface of the module, reduce the optical width of the shadowing ribbon by 45%. In the first part of this contribution, we present a simple coloring with white paint of the cell connectors [12], [13]. In comparison to textured cell connectors [9], the white colored ribbons work independently of the incident angles [12].…”

“…In the first part of this contribution, we present a simple coloring with white paint of the cell connectors [12], [13]. In comparison to textured cell connectors [9], the white colored ribbons work independently of the incident angles [12]. Thus, they show the same efficiency gain for tracked and nontracked systems.…”