Fig. 7
From: Developing design criteria for organic solar cells using well-absorbing non-fullerene acceptors
Simulation with optical interferences and collection losses. Device performance obtained by drift-diffusion simulations based on experimental optical data of a system with (a, c, e) complementary (PTB7-Th:FBR) and (b, d, f) congruent absorption (PTB7-Th:IDTBR). Optical simulations account for interference which leads to efficiency maxima at certain active layer thicknesses in (a) and (b). Different values of the electronic quality factor Q lead to qualitatively different thickness dependence. High Qs lead to higher gains in maximum efficiency for (a) complementary and (b) congruent absorption. The general increase in efficiency, evaluated at the optimum thickness, with higher Qs—meaning higher mobility and lower recombination coefficient—is further illustrated in (c) and (d). The attainable efficiency varies stronger with Q in the (c) complementary than in the (d) congruent case. For a large range of Qs in (e, f), the depicted optimum active layer thickness only takes discrete values around the interference maxima visible in (a) and (b). A transition to a higher optimum thickness requires lower Q values for (e) complementary than (f) congruent absorption
