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Combining Thickness Reduction and Light Trapping for Potential Efficiency Improvements in Perovskite Solar Cells

In this contribution it is shown that the efficiency of perovskite solar cells based on CH3NH3PbI3 can be increased further by combining thickness reduction of the perovskite layer and light trapping. A physical model for the current/voltage curve of pin solar cells is used to reveal the beneficial impact of thinning on cell efficiency. If interface recombination is kept at moderate levels, the model shows that there is a potential efficiency increase above 20% relative (+3% absolute) when thickness is reduced from 500 to 200 nm, provided total light absorption is maintained. A rigorous optical model is employed to calculate light absorption on typical state–of–the–art layer stacks patterned with sinusoidal grooves on ITO coated glass. The results suggest that solar light absorption in a flat, 500 nm thick film, can be matched by a 200 nm thick perovskite layer on a sinusoidal texture, while using 300 nm leads to several sinusoidal parameter combinations delivering the same light absorption. Since the structuring step must be compatible with low cost processing, it is shown that direct laser interference patterning (DLIP) is capable of delivering +3% absolute efficiency increase, while offering a typical photovoltaic module cost reduction of 10%.