This new type of photovoltaic device deserves attention.

1. Organic solar cell with 19.10% efficiency and 80.5% fill factor

Morphology plays a crucial role in charge generation and collection, thereby influencing the device performance of organic solar cells (OSCs). The pool of additives available for optimizing OSC morphology is limited, particularly for emerging layer-by-layer (LbL) OSCs, which hinders further improvements in photovoltaic performance.

Peng Qiang and Xiaopeng Xu, among others, from Sichuan University A new approach is reported, in which conjugated polymers are used as additives to optimize the morphology of the active layer, thereby enhancing the photovoltaic performance of LbL-OSCs. Four polymers—P-H, P-S, P-F, and P-Cl—with distinct side chains were synthesized.

Due to unfavorable energy-level alignment and detrimental molecular interactions, these polymers exhibit poor performance as both donor materials and additives in BHJ devices. In contrast, they can serve as effective additives for optimizing the PM6 fiber matrix, promoting the infiltration of BTP-eC9 and facilitating the formation of an interwoven D/A bicontinuous network with well-defined vertical phase separation.

This morphology was further optimized through side-chain engineering, leading to gradual improvements in charge separation and collection. The results show that adding a small amount of P-Cl as an additive to the PM6 layer, combined with the optimized morphology, yields a champion PCE of 19.10% and a fill factor (FF) of 80.5%.

https://onlinelibrary.wiley.com/doi/10.1002/adma.202208279

2. 19% Efficiency! Non-fullerene Acceptor Heterojunction Organic Solar Cells

The molecular architecture and aggregation behavior of non-fullerene acceptors (NFAs) are critical to their optical absorption, phase separation, and charge transport properties in bulk-heterojunction photovoltaic blends with electron donors, thereby determining the power conversion efficiency (PCE) of the corresponding organic solar cells (OSCs).

Wang Tao and others from Wuhan University of Technology The fibrous morphology of the small-molecule NFA L8-BO, facilitated by the fusion-ring solvent additive 1-fluoronaphthalenesulfonic acid (FN), was demonstrated, leading to a substantial enhancement in the device’s power conversion efficiency (PCE). Molecular dynamics simulations revealed that FN adsorbs onto the main chain of L8-BO, strengthening intermolecular packing along the conjugated backbone and thereby promoting the one-dimensional self-assembly of L8-BO into fine fibers with a compact polycrystalline structure.

L8-BO fibers were incorporated into a pseudo-body-heterojunction (P-BHJ) active layer using D18 as the donor, resulting in enhanced light absorption, charge transport, and charge collection. Consequently, the power conversion efficiency (PCE) of the D18/L8-BO binary P-BHJ blend increased from 16.0% to an unprecedented 19.0%, accompanied by a high fill factor of 80%. This work demonstrates a strategy for employing fibrillar NFAs to enhance the performance of organic solar cells.

https://onlinelibrary.wiley.com/doi/10.1002/adma.202208211

3. Tuning Charge Carrier Recombination in the Interfacial Layer to Enhance the Efficiency and Stability of Monolithic Perovskite/Organic Tandem Solar Cells

In single-junction solar cells, charge carriers can be efficiently extracted and collected by the electrodes, resulting in minimal charge-carrier accumulation and low energy losses (E _loss ). However, in tandem solar cells (TSCs), achieving a balance between the hole and electron densities extracted from the two respective subcells to facilitate efficient recombination at the interconnect layer (ICL) poses a significant challenge.

Li Yaowen and others from Soochow University A charge–carrier–dynamic management strategy for inorganic perovskite/organic TSCs is proposed. This strategy focuses on simultaneously tuning CsPbI _1.9 Br _1.1 Defect states in perovskite solar cells and the hole transport capability from the perovskite layer to the interfacial charge-transport layer. The target hole density on the perovskite surface and the pre‑ICL hole loss are significantly enhanced.

As a result, the hole/electron density offset within the ICL can be effectively reduced, leading to balanced charge carrier recombination, which in turn lowers the E in the TSC. _loss . The resulting inorganic perovskite/organic 0.062-cm ² The TSC exhibits a remarkable power conversion efficiency (PCE) of 23.17% and an ultra-high open-circuit voltage (Voc) of 2.15 V. _oc ), and 1.004 cm ² The device’s PCE of 21.69% exhibits weak size dependence. Furthermore, this charge-carrier dynamic management strategy can also effectively enhance the UV stability of TSCs.

https://doi.org/10.1002/adma.202208604

4. 19.12% Efficiency! All-Purpose, Low-Cost Polymer Solar Cells Based on 4-Chlorothiazole

Thanks to the emergence of narrow-bandgap small-molecule acceptors (SMAs), particularly the “Y” series, the power conversion efficiency (PCE) of polymer solar cells (PSCs) has increased rapidly. However, with the exception of PM6 and D18, high-performance, easily synthesized, and broadly applicable polymer donors remain relatively scarce.

Min Jie and others from Wuhan University Based on 4-chlorothiazole derivatives, two structurally simple polymer donors, PTz3Cl and PBTTz3Cl, were designed and synthesized. Compared with PTz3Cl, PBTTz3Cl exhibits slightly weaker intermolecular interactions; when blended with the SMA L8-BO, the resulting OSCs achieve a power conversion efficiency (PCE) of 18.38%. This is attributed to the stronger donor–acceptor interactions between PBTTz3Cl and L8-BO, which promote an optimal phase-separated morphology.

Further studies revealed that PBTTz3Cl exhibits excellent photovoltaic performance when paired with a wide range of small-molecule acceptors, underscoring its broad applicability. Building on these findings, ternary PSCs were designed, in which BTP-eC9 was introduced as the guest material into the PBTTz3Cl:L8-BO host system. Owing to the further optimized blend morphology and more balanced charge transport, the power conversion efficiency (PCE) increased to 19.12%, one of the highest values reported for PSCs. This work presents a novel, low-cost electron-deficient unit design for constructing highly versatile, high-performance polymer donors.

https://onlinelibrary.wiley.com/doi/10.1002/adma.202208750

5.  18.14% record Efficiency! Ternary All-Polymer Solar Cells Fabricated via Two-Step Sequential Deposition

Achieving fine-tuned active-layer morphologies with appropriate vertical phase separation to enhance charge generation and charge transport has long been the primary goal in the pursuit of high-efficiency all-polymer bulk-heterojunction (BHJ) solar cells (all-PSCs).

Min Jie and others from Wuhan University A solution is proposed that synergistically integrates a ternary blending strategy with the layer-by-layer (LBL) assembly process. By incorporating a highly crystalline synthetic polymer acceptor, PY-Cl, into the designed host–acceptor system PY–SSe–V, the vertical phase distribution and molecular ordering in LBL-type ternary all-PSCs can be significantly improved, outperforming those in LBL-type PM6/PY–SSe–V binary all-PSCs.

The formation of a high-quality bulk microstructure not only facilitates charge transport and extraction but also reduces energetic disorder and non-radiative recombination losses, thereby simultaneously enhancing all three photovoltaic parameters. Consequently, the PM6/(PY-SSe-V:PY-Cl) ternary all-PSCs achieve a record efficiency of 18.14%, one of the highest values reported to date for all-PSCs. This work presents a simple yet effective LBL-based ternary strategy for realizing high-efficiency all-PSCs.

https://onlinelibrary.wiley.com/doi/10.1002/adma.202209350