Predicted Power Output of Silicon-Based Bifacial Tandem Photovoltaic Systems

Combining the higher energy yield of bifacial photovoltaic modules with the higher efficiency of silicon-based tandem devices is a promising pathway to reduce the levelized cost of electricity of photovoltaic systems. In a two-terminal bifacial tandem, the additional photon flux on the back of the bottom cell alters the current matching between the cells. This study quantifies this phenomenon, starting with spectrally resolved front and back irradiances determined from ray tracing under realistic conditions. A tandem-device model is then used to explore the impact of different scenarios on the optimal top-cell bandgap and power production. Although the energy gains from bifacial tandem systems are small, the range of suitable top-cell bandgaps is greatly broadened, thus widening the window of absorber candidates. In one exemplary case, a bifacial tandem with a top-cell bandgap as low as 1.63 eV retains the energy output of an optimized monofacial tandem with a 1.71-eV top cell. [Display omitted] •Bifacial tandem photovoltaic systems were modeled under different scenarios•The impact of bifaciality on the current matching between the cells was studied•Although energy gains are small, the range of top-cell materials greatly widens The energy yield of photovoltaic systems is an important lever to reduce their levelized cost of electricity. Pathways that can be pursued in parallel include increasing the efficiency of individual cells through tandem architectures, increasing the normal irradiance on modules through tracking, or increasing the total irradiance with bifacial modules. Here, through simulation, we investigate the interplay between bifaciality and series-connected tandem architectures—where the top and bottom cells are current-matched—with and without tracking. Although modest gains are achieved with bifacial tandem systems compared with monofacial tandem ones, the range of appropriate top-cell bandgaps widens. This opens a pathway to using lower-bandgap, higher-performance top-cell material candidates without a detrimental impact on the current matching between the cells. The energy yield of photovoltaic systems can be augmented by increasing the efficiency of individual cells through tandem architectures, increasing the normal irradiance on modules through tracking, or increasing the total irradiance with bifacial modules. Here, we investigate bifaciality in series-connected tandem architectures and find modest energy gains relative to their monofa