Nonradiative Energy Loss Generated by Two Hidden Trade-Offs in Non-Fullerene Organic Solar Cells with the Positive Correlation between J_SC and V_OC

Abstract

Non-fullerene organic solar cells (OSCs) achieve the simultaneous enhancement of short-circuit current density (J SC ) and open-circuit voltage (V OC ), which will be defined as positive correlation in this work. However, it has not ushered in a breakthrough of power conversion efficiency (PCE). We reveal that the essence lies in two hidden trade-offs, issued from the two-sidedness of electronic coupling (V el ) and thus resulting in the competition between the increasing magnitudes of J SC and V OC . A great V el could improve the energy of the charge-transfer state, leading to a phenomenon called positive correlation. Nevertheless, it also induces the large nonradiative energy loss and is adverse to the increasing magnitude of J SC or V OC simultaneously, limiting the great improvement in PCE. Overall, we reveal the qualitative change point of trade-offs in non-fullerene OSCs by the quantitative change of microscopic difference under the loss pathway.

Advancements in Organic-Based Hybrid Tandem Solar Cells Considering Light Absorption and Spectral Matching of Organic Materials

“…This enhanced hybridization in low Δ E CT systems results in high EQE EL . Recent studies have reported that EQE EL increases as HOMO offset decreases or in lower Δ E CT systems, leading to a reduction in Δ E nonrad . − In particular, the PM6:Y11-based OSC with a Δ E CT of 0 eV achieved a low Δ E nonrad of 0.17 eV owing to a high EQE EL of 1.4 × 10 –3 . Furthermore, the overall E loss of the PM6:Y11-based OSC ranges from 0.43 to 0.51 eV, closely resembling that of crystalline silicon (c-Si) solar cells (0.38 eV) …”