Volatile Solid Additive‐Assisted Sequential Deposition Enables 18.42% Efficiency in Organic Solar Cells

Abstract

Morphology optimization of active layer plays a critical role in improving the performance of organic solar cells (OSCs). In this work, a volatile solid additive‐assisted sequential deposition (SD) strategy is reported to regulate the molecular order and phase separation in solid state. The OSC adopts polymer donor D18‐Cl and acceptor N3 as active layer, as well as 1,4‐diiodobenzene (DIB) as volatile additive. Compared to the D18‐Cl:N3 (one‐time deposition of mixture) and D18‐Cl/N3 (SD) platforms, the D18‐Cl/N3(DIB) device based on DIB‐assisted SD method exhibits a finer phase separation with greatly enhanced molecular crystallinity. The optimal morphology delivers superior charge transport and extraction, offering a champion power conversion efficiency of 18.42% with significantly enhanced short‐circuit current density (Jsc) of 27.18 mA cm−2 and fill factor of 78.8%. This is one of the best performances in binary SD OSCs to date. Angle‐dependent grazing‐incidence wide‐angle X‐ray scattering technique effectively reveals the vertical phase separation and molecular crystallinity of the active layer. This work demonstrates the combination of volatile solid additive and sequential deposition is an effective method to develop high‐performance OSCs.

Optimizing sequence structures by stepwise-feeding terpolymerization for high-performance organic solar cells

“…We have estimated the hole mobility (m h ) and electron mobility (m e ) with the hole-only (ITO/PEDOT:PSS/polymer:Y6/ MoO 3 /Ag) and electron-only devices (ITO/ZnO/polymer:Y6/ PDINN/Al), 20,21 respectively. In comparison with the m e /m h values of 3.22 Â 10 À4 /5.49 Â 10 À4 cm 2 V À1 s À1 , 3.63 Â 10 À4 /5.09 Â 10 À4 cm 2 V À1 s À1 , 2.42 Â 10 À4 /4.83 Â 10 À4 cm 2 V À1 s À1 , 4.62 Â 10 À4 cm 2 V À1 s À1 /5.20 Â 10 À4 cm 2 V À1 s À1 and 3.19 Â 10 À4 /5.40 Â 10 À4 cm 2 V À1 s À1 for D18:Y6, H6:Y6, H7:Y6, H8:Y6 and H10:Y6-based devices, the H9:Y6-based device exhibits higher mobility values and more balanced m e /m h with 4.68 Â 10 À4 /5.01 Â 10 À4 cm 2 V À1 s À1 , respectively (Fig.…”

An unfused-ring acceptor enabling ∼12% efficiency for layer-by-layer organic solar cells

“…Layer-by-layer (LBL) deposition processing has been demonstrated as an efficient method to boost OSC performance by collaboratively manipulating the microscopic phase separation and component distribution. [20][21][22] Furthermore, sequentially depositing donor and acceptor layers via the LBL method makes it possible to regulate the donor and acceptor individually, thus reducing the processing complexity of OSCs to a certain extent. [23][24][25] For example, Song and co-workers fabricated PM6/BTP-eC9 OSCs via the spin-coating LBL process to achieve an optimal PCE of 17.13%.…”

Can Organic Solar Cells Beat the Near-Equilibrium Thermodynamic Limit?

“…Composition gradients in OPV have been investigated in some detail, both in experiments 23 − 36 and simulations. 23 , 37 , 38 These studies aimed for improved charge transport and reduced leakage currents based on the idea that a compositional gradient effectively propels electrons and holes to their corresponding electrodes.…”

“… 25 The topic of composition gradients gained additional urgency with the very recent advances in OPV performance made through sequential deposition of the donor and acceptor compounds. 32 − 36 Apart from being robust, this processing technique is prone to lead to strong composition gradients, the effect of which so far lacks a formal interpretational framework. With the exception of the work by Andersson and Kemerink, 22 simulations of graded OPVs only utilized drift-diffusion models, neglecting both slow relaxation processes and morphology aspects, and did not lead to a consistent physical picture.…”

“…Specifically, we speculate that the spontaneous phase separation occurring in stratified D:A films, as, e.g., produced by sequential deposition of donor and acceptor compounds, will lead to funnel-like networks that resemble those considered here. 33 , 44 , 45 However, for these bottom-up funnels to be maximally effective, both the degree of stratification and the length scale of lateral phase separation will have to be optimized.…”