研究目的

To analyze the influence of front cell and back cell bandgaps and use transfer matrix modeling to rationally design and optimize effective tandem solar cell structures before actual device fabrication.

研究成果

We present a methodology to estimate the maximum possible PCE produced by tandem solar cell devices as a function of the front cell and back cell bandgap and a method to model the JSC produced by tandem devices based on the absorption coefficients of real materials. Given the performance limitations of known materials, we consider the particular case in which PTB7‐Th is used as a back cell material. Given a Vloss of 0.8 V, which is typical of benchmark, wide bandgap PSC materials we find that the optimal absorption onset of front cell material, based on a PTB7‐Th back cell, is about 680 nm. Two front cell materials, PDTBTBZ‐2F and PBTDT, which possess absorption onsets close to this ideal value, are explored in real devices. With the aid of TM modeling, we identify optimal device architecture and processing conditions to produce the largest possible JSC. Thorough device optimization leads to JSCs which are consistent with TM modeling. Additional optimization of the recombination layer was able to improve the tandem FFs up to 0.74, which exceeded our expectations and yielded PCEs of up to 12.8%, which is among the highest PCE values reported to date for fullerene‐based tandem devices. We believe that the methodology described in this study will be of great utility to other researchers to aid in the rational design and efficient optimization of tandem solar cell devices.

研究不足

The technical and application constraints of the experiments, as well as potential areas for optimization.