As single junction photovoltaic (PV) technologies, both Si heterojunction (HIT) and perovskite based solar cells promise high efficiencies at low cost. Intuitively, a traditional tandem cell design with these cells connected in series is expected to improve the efficiency further. Using a self-consistent numerical modeling of optical and transport characteristics, however, we find that a traditional series connected tandem design suffers from low JSC due to band-gap mismatch and current matching constraints. Specifically, a traditional tandem cell with state-of-the-art HIT (η=24%) and perovskite (η=20%) sub-cells provides only a modest tandem efficiency of ηT∼ 25%. Instead, we demonstrate that a bifacial HIT/perovskite tandem design decouples the optoelectronic constraints and provides an innovative path for extraordinary efficiencies. In the bifacial configuration, the same state-of-the-art sub-cells achieve a normalized output of ηT* = 33%, exceeding the bifacial HIT performance at practical albedo reflections. Unlike the traditional design, this bifacial design is relatively insensitive to perovskite thickness variations, which may translate to simpler manufacture and higher yield.

Photovoltaic (PV) cell technology has made great progress over the past few decades, bringing the PV energy cost down to a point where it is competitive to conventional electricity prices. While monofacial panels have historically dominated the market, recent developments in the manufacturing of bifacial panels (collecting light from both faces) have made them accessible for commercial applications. It is therefore imperative to define the design principles so that the steeply expanding market of bifacial modules and PV farms stays on an efficient path. In this paper, we will discuss physics-based models for these next-generation bifacial PV farms for analyzing yield and costs. Besides the conventional farm configurations, tracking systems are gaining market shares aiming to enhance the yield at a lower cost. Within ± 30 ∘ latitudes, we predict a 20%-30% energy gain for fixed-tilt bifacial over monofacial modules and an additional 20%–40% gain for single-axis bifacial tracking. Compound systems such as agrophotovoltaics and floating PV applications may be the possible future for a sustainable merger of food-water-energy systems. We show a competing relation between active light collection on crops and energy yield in an agrophotovoltaics system vs panel density—the final design will be decided by the crop yield or light usage efficacy constraint. The output reliability in terms of soiling and module degradation is also explained in this paper. Solar farms are expected to see 2%–5% loss in revenue in Asia and the Middle East even after optimal cleaning. Additionally, the bifacial modules degrade ∼0.5%–0.6%/year. While there have been several physics-based degradation analyses, the bifacial technology lacks a large enough data set of long-term degradation studies for accurate predictions. The combined economics of reliability against yield will decide the viability of the next generation bifacial PV industry.

The bifacial photovoltaics (PV) technology promises several advantages over monofacials, including improved energy yield, lower operating temperature, and easier integration with agrophotovoltaics. There have been various experimental or computational studies comparing bifacials to monofacials; however, a theory-experiment combined analysis for accurate worldwide extrapolation is missing. Literature review reveals that many reported experiments study standalone systems that overrepresent the yield performance obtainable in farms. Moreover, most reported experimental studies are for configurations that are not necessarily designed close to the optimum. In this work, we experimentally study and analyze the fixed-tilted bifacial farm configiurations, namely south-facing monofacial, south-facing tilted bifacial (TBF), and ground-sculpted vertical bifacial (VBF) arrays, at Dhaka, Bangladesh (23.7 °N, 90.4 °E). The optimal TBF configuration, for 0.5 albedo, yields 21.3% and 73.3% more than the optimal monofacial and the optimal VBF configurations, respectively. Through a combination of experimental and numerical analysis, we compare the in-array performance of the configurations under different albedo conditions to analyze the physics and consolidate the predictions. There is a growing interest in PV array configurations beyond the conventionally ground-mounted south-facing TBF, such as agrophotovoltaics, floating-PV, industry-roof PV array, etc. This necessitates a critical analysis of various array configurations for broader PV expansion.

Bifacial tandem cells promise to reduce three fundamental losses (i.e., above-bandgap, below bandgap, and the uncollected light between panels) inherent in classical single junction photovoltaic (PV) systems. The successive filtering of light through the bandgap cascade and the requirement of current continuity make optimization of tandem cells difficult and accessible only to numerical solution through computer modeling. The challenge is even more complicated for bifacial design. In this paper, we use an elegantly simple analytical approach to show that the essential physics of optimization is intuitively obvious, and deeply insightful results can be obtained with a few lines of algebra. This powerful approach reproduces, as special cases, all of the known results of conventional and bifacial tandem cells and highlights the asymptotic efficiency gain of these technologies.