TY  - JOUR
AU  - Kaienburg, Pascal
AU  - Krückemeier, Lisa
AU  - Lübke, Dana
AU  - Nelson, Jenny
AU  - Rau, Uwe
AU  - Kirchartz, Thomas
TI  - How solar cell efficiency is governed by the αμτ product
JO  - Physical review research
VL  - 2
IS  - 2
SN  - 2643-1564
CY  - College Park, MD
PB  - APS
M1  - FZJ-2020-02494
SP  - 023109
PY  - 2020
AB  - The interplay of light absorption, charge-carrier transport, and charge-carrier recombination determines the performance of a photovoltaic absorber material. Here we analyze the influence on the solar-cell efficiency of the absorber material properties absorption coefficient α, charge-carrier mobility μ, and charge-carrier lifetime τ, for different scenarios. We combine analytical calculations with numerical drift-diffusion simulations to understand the relative importance of these three quantities. Whenever charge collection is a limiting factor, the αμτ product is a good figure of merit (FOM) to predict solar-cell efficiency, while for sufficiently high mobilities, the relevant FOM is reduced to the ατ product. We find no fundamental difference between simulations based on monomolecular or bimolecular recombination, but strong surface-recombination affects the maximum efficiency in the high-mobility limit. In the limiting case of high μ and high surface-recombination velocity S, the α/S ratio is the relevant FOM. Subsequently, we apply our findings to organic solar cells which tend to suffer from inefficient charge-carrier collection and whose absorptivity is influenced by interference effects. We estimate that a modest increase in absorption strength by a factor of 1.5 leads to a relative efficiency increase of more than 10% for state-of-the-art organic solar cells.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000602780200009
DO  - DOI:10.1103/PhysRevResearch.2.023109
UR  - https://juser.fz-juelich.de/record/877889
ER  -