Optimization of perovskite/c-Si tandem module for energy yield maximization under real-world conditions

Abstract

Tandem technology has emerged as one of the most promising innovations in the field of photovoltaics. Higher conversion efficiencies than standard single-junction cells have already been achieved. Proving how these laboratory conversion capabilities translate into real-world performance is therefore a main interest drive within the photovoltaic research community.

Typically, photovoltaic device performance is assessed in Standard Test Conditions (STC). For the majority of climates, this is however not representative of actual operating conditions. With the aim of studying potential system applications, the energy yield prediction method adopted in this thesis analyzes tandem technology performance considering real-world conditions. For this scope, the PVMD Toolbox for PV system modeling is employed.

The tandem device investigated in this work is a perovskite/c-Si based structure in a two-terminal architecture. In particular, a TU Delft own poly-SiOx based crystalline silicon bottom cell is utilized in the configuration. This structure is implemented in the Toolbox to carry out Optical simulations from cell to module system level. Operating conditions are introduced through use of the Toolbox Weather and Thermal models. These recreate real-world illumination and climate settings for the selected locations of Reykjavik, Rome and Alice Springs. With an STC-optimized perovskite thickness of 515 nm, the hourly implied photocurrent density of the device is calculated and validated. The jph annual average is 1.92, 3.34 and 5.01 mA/cm2 for the three locations, respectively. These values take into account a sub-cells current mis-
match loss between 5 and 8% depending on location. To reproduce real-world cell electrical parameters behavior, the variable irradiance and temperature sub-cells J-V curves have been obtained. A poly-SiOx based silicon prototype was tested in laboratory settings and its curves then utilized in simulations after measurements validation.

The module annual energy yield is computed through simulations with the Toolbox Electric model. In terms of specific DC yield, the STC-optimized module delivers 820, 1,427 and 2,161 kWh/kWp/year in the three locations. The power mismatch lowering effect due to the fill factor gain compensates the current mismatch in this 2T configuration, reducing energy mismatch losses. This performance is then compared to a reference single-junction poly-SiOx based silicon module, to show how tandem technology potentially outperforms standard modules differently depending on climatic conditions. The tandem module is also assessed in terms of DC performance ratio (PR), exhibiting values over 0.94 for all three locations. The structure is then real-world optimized by varying perovskite thickness, with the goal of maximizing
location-specific energy yield and PR. Slight improvements are obtained for the Reykjavik and Alice Springs locations, where the energy yield increases by few relative percentage points along with PR.