Optical and electrical optimization of all-perovskite pin type junction tandem solar cells

Abstract

A definitive breakthrough of perovskite solar cells towards large scale industrialization is believed to be the demonstration of higher efficiencies than conventional silicon technology, suggesting the exploration of perovskite tandem cell configurations. Since high efficiency tandem solar cells require careful optimization of photoactive as well as contact and additional functional layers, we propose an optical-electrical model to obtain the optimum layer thicknesses and the attainable electrical output parameters of two-terminal perovskite-perovskite tandem solar cells. The optical model takes into account the coherent propagation of light through the layer stack comprising two perovskite semiconductors and the corresponding contact layers, while the electrical model assumes two series-connected analytical current/voltage equations for pin solar cells. This model allows to assess the impact of the main physical parameters on each perovskite layer without requiring the high specificity needed in more rigorous numerical simulations. Efficiencies above 34% are predicted considering available perovskites with non-optimum bandgap and contact materials already proven in efficient laboratory solar cells. The requisite to attain such efficiencies is that recombination at the interfaces between the perovskite and contact materials is kept low in both bottom and top cells. Furthermore, within the assumption of non-optimum bandgaps of currently available perovskites, the simulation results suggest that efficiencies around 37% are possible when adopting contact materials with smaller absorption, more adequate refraction indices, and lower resistivity.

Accounting for Fabrication Variability in Transparent Perovskite Solar Cells for Four‐Terminal Tandem Applications

“…Several mathematical models have been developed and solved [ 15–26 ] to quantify and optimize the efficiency and optoelectronic properties of perovskite‐based tandem devices. In these models, the optics are solved with either a one‐dimensional transfer matrix method for tandem devices with planar interfaces [ 15–17,19,21,24–27 ] or with two‐dimensional ray tracing for textured interfaces in the silicon bottom cell. [ 18,20,22 ] The current–voltage characteristics are modeled with either semiconductor physics [ 15–17,23–25 ] or equivalent circuits [ 19–22 ] for both subcells.…”

“…Good candidates for the bottom cell are solar cells made of silicon, [1][2][3][4] narrow bandgap perovskite, [5][6][7][8] CIS, [9,10] and CIGS. [11][12][13][14] Several mathematical models have been developed and solved [15][16][17][18][19][20][21][22][23][24][25][26] to quantify and optimize the efficiency and optoelectronic properties of perovskite-based tandem devices. In these models, the optics are solved with either a one-dimensional transfer matrix method for tandem devices with planar interfaces [15][16][17]19,21,[24][25][26][27] or with two-dimensional ray tracing for textured interfaces in the silicon bottom cell.…”

“…[11][12][13][14] Several mathematical models have been developed and solved [15][16][17][18][19][20][21][22][23][24][25][26] to quantify and optimize the efficiency and optoelectronic properties of perovskite-based tandem devices. In these models, the optics are solved with either a one-dimensional transfer matrix method for tandem devices with planar interfaces [15][16][17]19,21,[24][25][26][27] or with two-dimensional ray tracing for textured interfaces in the silicon bottom cell. [18,20,22] The current-voltage characteristics are modeled with either semiconductor physics [15][16][17][23][24][25] or equivalent circuits [19][20][21][22] for both subcells.…”

“…[ 18 ] There are also modeling studies focusing on the operating conditions of the tandem device, such as quantifying the irradiance and temperature variations to the annual energy yield of the device [ 19 ] and identifying the device architecture that is less sensitive to temperature variations. [ 15 ] Most of these modeling studies either quantified the optimal layer thickness for the different materials in the perovskite cell to achieve the highest device efficiency by varying one factor at a time (OFAT) [ 16,23,25,26,28 ] or through multiparametric optimization. [ 22,24,29 ] Common to all these modeling studies is the assumption that the material properties of the perovskite layer are independent of the perovskite layer thickness.…”

Preparation of thin films of molecule-based magnets for optical measurements

“…Analogously, the field of molecular photovoltaics faces a similar issue: the stacking of different materials gives rise to unwanted reflection at each of their interfaces when the refractive index for each layer is poorly matched, thus decreasing the light harvesting potential of the device. The workaround to this is selection of materials that possess similar enough refractive indices whilst still retaining their primary functionality, such as charge transport properties [39]. This approach could equally be applied to thin films of PBAs: by selecting an encapsulating agent of appropriate optical properties and applying this to the surface of the film, any voids on the rough polycrystalline surface will be filled and the number of air-crystallite boundaries decreased, thus decreasing the propensity for scattering events to occur.…”